Your way is certainly quite streamlined, seems easy as well. I bought an aquarium air pump for that issue, slow as hell but it certainly works since I just leave it running on the sink counter. I just clean the hole, dry as well as I can with paper towels then stick the pump hoses in the canal. I did buy the cheapest/shittiest one, so that is why it is presumably slow to dry.
Id try and get it more uniform finish before going in. Also, I've found that using a fish tank aerator thingy helped with better uniformity.
This is what I went with, cheap and works well. HIRALIY Aquarium Air Pump, Fish Tank Air Pump with Dual Outlet Adjustable Air Valve, Ultra Silent Oxygen Fish Tank Bubbler with Air Stones Silicone Tube Check Valves Up to 100 Gallon Tank https://www.amazon.com/dp/B0854CWH5M/ref=cm_sw_r_apan_i_3KV0W02ZRPHQFT3HB8AK?_encoding=UTF8&psc=1
It's a Hiraliy air pump I got from Amazon that came with a lot of accessories such as airstones and airline tubing. It's quiet if it's suspended, and claims to be suitable up to 100 gallons. I believe it, since the knob is nowhere near full power.
Check it out: link
HIRALIY Aquarium Air Pump, Fish Tank Air Pump with Dual Outlet Adjustable Air Valve, Ultra Silent Oxygen Fish Tank Bubbler with Air Stones Silicone Tube Check Valves Up to 100 Gallon Tank https://www.amazon.com/dp/B0854CWH5M/ref=cm_sw_r_awdo_1K5S9N6DEM3164MKPWJR
I really like this one from Amazon (only thing it didn’t come with was the sponge filter but I got extra tubing , extra air stones and check valves ) ! It’s also very quiet to me but I’m a newbie and I have it on the lowest setting for my betta.
I've bought mine on Amazon, and had no issues. Petco is selling them now, which is nice. With a betta, definitely get an air pump with an adjustable flow. I like this one: HIRALIY Aquarium Air Pump, Fish... https://www.amazon.com/dp/B0854CWH5M?ref=ppx_pop_mob_ap_share
It's hard to tell from the pics but the roots in the vase do look potentially rotted. Are they mushy? Do they smell a bit off? If so I would cut them off here: https://imgur.com/a/AZNsCY5 and place the plant in water, put it in a nice bright spot and wait for it to root. Pothos are pretty resilient so you should have roots in a few weeks or less, but if you want to speed up the process you can buy some rooting hormone and maybe a small air stone pump (like the kind used in aquariums ) . 10% fertilizer sounds high to me - do you mean organic fertilizer like worm castings? Or granules? Either way, you could probably change that to standard potting mix (or just replace that 10% with more coco coir) and liquid fertilize as needed.
I've bought many sponge filters and air pumps off of Amazon and they've been great. Get a pump that's adjustable so you can keep the flow low.
Pump: HIRALIY Aquarium Air Pump, Fish... https://www.amazon.com/dp/B0854CWH5M?ref=ppx_pop_mob_ap_share
Sponge: https://www.amazon.com/dp/B06Y5Z6V8Z?ref=ppx_pop_mob_ap_share
this is what I use
https://www.amazon.ca/gp/product/B0854CWH5M/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
It seems strange considering how soft the air blows through but continuous air overnight will dry it out completely, every time. You just have to make sure you insert the tube just before the very back of the tunnel so the flow doesn't get blocked. You should be able to feel the air coming out with your nose.
This one has two airflows so you can use it for both holes.
That won't be enough water for them once they get bigger. The biggest one will probably eat all the others pretty quickly.
If you do want to try it indoors, I've found this air pump is very quiet. I sleep about 6 ft away from it and can't tell it's on: https://www.amazon.com/gp/product/B0854CWH5M/
You can pair that with one of these: https://www.amazon.com/gp/product/B08H7MBRYB/
this one works for me.