I'd like to just go over how I taught my dog about scents in Nosework. We've been doing Nosework since my pup was about 6 months old (she's 2.5 now). I didn't want to trial my dog, mostly because I don't make very much money, and I was really just in the sport for the fun, but I got her ORT (odor recognition test, which is the first step to trialing) anyway, and she passed with flying colors.
Instead of just using the scent and hoping my dog found it different/interesting enough to target, we started with food.
I started with a line of boxes, and one box (source) had several REALLY smelly treats inside. Things like hotdogs, <strong>these</strong> are literally the smelliest dog treats I've ever used, sausage, bacon, etc. Stinky things.
Then I would hold my pup behind the start line by her back hooking harness, and say "find it!" and let go. She would run around sniffing each box, and when she found the one with food, I would just open the box and let her eat it.
After doing this several times while moving the "source" box around (NOT PUTTING FOOD IN DIFFERENT BOXES, you do not want to make other boxes smell like food or you are setting yourself up for failure) I then added the scent to the box with the food.
You see, dogs compartmentalize scents. When we smell chicken noodle soup, your dog smells chicken, broth, carrots, celery, pepper, rice, etc. They smell each thing individually. This means when you pair food with scent, the dog smells food and then scent, not the combination of food/scent.
Pairing is very important in Canine Nosework. It can really help your dog target for longer, which is what you want when trialing.
So you pair the food and the scent for a while, the dog targets both, and receives the treats. Then, you use less and less smelly treats as time goes on, and you reward the dog with the really smelly treats instead of pairing with them.
Eventually, you eliminate the treats and see if your dog still targets the scent, which they will if you worked slow enough to build up to this point. When they target the scent, you need to very quickly swoop in and reward whether they are holding their nose onto the scent or not. This is key, because if you wait too long, your dog will think to herself, "this must not be right." Don't allow your dog to doubt themselves until you are 100% positive your dog will say to you, "NO THIS IS WHERE THE SCENT IS YOU IDIOT!" -- it takes a TON of work to get to that point.
So you're doing box work with the scents, and your dog is reliably hitting the scent and you are rewarding rapid fire. Great! Then you move on to pairing the first scent you used (we started with just birch) with a second scent (anise). Just like you paired food with the scent, you are teaching your dog to target the new scent by pairing it with the old scent and having your dog target both. Like I said, they compartmentalize scents, so they will be able to target both scents separately in a short period of time.
Okay so let's say your dog is now targeting all three scents separately, that's awesome! What you want to do now is work on building up the targeting. It's important that a dog target the scent. For this, we will often go back to pairing, and use something like cheese whiz, or peanut butter, or cream cheese to get the dog to lick the hide/hold their nose there so you can swoop in to reward.
After about a year of training, we finally started playing "red-light green-light" where the dog would find the scent, we would begin to approach the dog, but if the dog pulled their nose away from the source to look at us, we would immediately freeze. They would re-target, and we would move in again quickly, but if they looked up we'd freeze. This is a great way to get the dog to target the scent for longer, but you have to be confident that your dog understands the game 100% first. If your dog wanders off when you play this game, they weren't ready for it.
Another thing we'd do is use oddly shaped boxes and put them in weird places. We'd hang one from the ceiling, or place a few on chairs, or tables, or underneath things. This helps the dog generalize.
Then we started doing box work outdoors. When you go outdoors intially, you want to go back to pairing to make it a lot easier for the dog to understand it's the same game as you were playing indoors. The boxes are a pretty clear indicator, but the pairing helps for very distracted dogs.
While working on box-work outdoors, we were working on invisible hides indoors where the dog would need to find the scent stuck underneath a chair, or behind a toilet, instead of in a box. This is easy peasy if your dog understands the game already.
After a while of working from square one outdoors, we started doing invisible hides, and then indoors we would work on blind hides (blind from us humans. We didn't know where the hides were, we just had to trust our dogs body language).
Outdoors we could work on things like placing scent in puddles (yes dogs can smell the scent in REALLY deep water), and in cracks in the ground so the dog would be thrown off by the scent traveling up the crack.
Then we started doing out of reach hides where the dogs would need to target a hide they couldn't reach with their noses. Some dogs has a lot of trouble with this, not my hound dog!
Then we started doing car searches. In trials, car searches are the regular. My dog loved doing car searches! She still sniffs cars when we pass by them on our walks juuuuust to make sure ;)
All along we always go back to pairing, and box work. We do this randomly just to keep the dogs feeling successful/understanding targeting. Going back to box work and pairing does not mean your dog is struggling with Nosework, and you should never feel bad about going back often. We always pair every few hides with treats, and we always go back to box work a few times a week. It's just important to keep the game really fun and basic for your dog!
Lastly (and we're not at this point yet) what my instructor does (she is NACSW official) is place food like burgers, pizza, chicken, french fries, etc, in boxes, and then puts scent in one box. The dog has to target the scent, and NOT the food. This is super challenging, and like I said, this is like NW3 stuff, we're totally not there yet lol.
For the record, I like the idea of crating the dogs in between scent work. A lot of people here are disagreeing with it, and saying it's just too much work, or too stressful for the dog, but in fact, the opposite tends to be true. Dogs need a "reset" moment, a break. They need to work the scent, find it, be rewarded for it, and then get some down-time to really let it all sink it. If they're just going from hide to outside hide to indoor hide to hide to hide to walking around to this to peeing to that to hide to hide... that's just WAY too overstimulating, and way too much. Having a nice little break in between each hide will really help it all sink it, and get them very excited for the next hide. In my opinion, the dog needs to know that once they are let out of the crate and the working harness it put on, it's TIME TO WORK/SEARCH. The down-time helps build a drive to work in my opinion.
If you have any random little questions I can maybe help answer them! Nosework is my faaaavorite dog sport, and I've been working under and official certified NACSW instructor for a couple of years now/going to trials/ORT's.