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I have this lying around and like it. Torch. For “fire starters” a paper towel or 2 soaked in a bit of cooking oil is about as as cheap as you can get, and works well.
This is what I prefer in addition to my cast iron pan for certain things (I don't torch skinless chicken breast) - Iwatani culinary torch - It sounds like a fighter jet
Salt, pepper, garlic powder, cayenne pepper (just a tiny bit) with dry thyme and rosemary in the bag, didn't have any of the fresh stuff.
The sear was just with a simple butane kitchen torch. I normally do torch and pan with oil and butter sear but was being lazy and didn't want to clan another pan.
Edit: The torch i used
You're going to need a torch as well. I highly recommend you get this Iwatani torch from Amazon - http://www.amazon.com/Iwatani-Cooking-Torch-Professional-Culinary/dp/B00BBJC1CY/ref=sr_1_1?ie=UTF8&qid=1461172630&sr=8-1&keywords=iwatani+torch
It doesn't get "refilled" like you do with most creme brulee torches, you just pop on a new can of super cheap portable stove butane that you can pick up at just about any hardware store. I've had mine for 3 years now and it lights every time. And no leaking or starter issues like I've had with just about every other torch I've used.
I did the blowtorch thing for a while. Didn't really like the results. I had one of these and it would take forever to make any impact on beef, pork, or chicken. It worked well for fish.
This is the one I got from Amazon and it just connects to a big canister of butane you can also get from Amazon. The canisters seem to last a long time because I bought a three pack awhile ago and the one I am using still feels really full.
As the other posters have said, 139.5 is too high for an end result of medium if you are going to sear in pan or grill to finish. Either of those methods are going to add a good bit of additional heat to the steak.
I would recommend trying 131 degrees if you are going to use the sear method you described. I prefer medium rare, and have my steaks at 125 and then sear hard and get a good medium rare result.
If you want something that doesn't transfer as much heat into the meat, you can try finishing with a torch. Allows a crust formation with almost no additional cooking inside the meat. I have this one. Some people taste uncombusted fuel with the torch method, your mileage may vary. I prefer my steaks seared in pan, but use the torch on other things like lamb and lobster.
Hey if it works for you then who am I to tell you you're doing it wrong?
I prefer a rare steak and usually shoot for a water bath at 131F for about an hour and a half followed by a quick sear with my Iwatani blow torch. I'd guess the torch does less cooking than a short fry in oil does. My absolute favorite is to finish it off over some screaming hot charcoal but that isn't an open for me right now in the city.
its 25 at amazon right now. I know its above your max.
That torch is pretty decent, but I prefer this one
here I use it for sous vide, but it's small, long-lasting, and to refill you just get new canisters.