I know of blogs like Good Guy Dan that have a lot of gunpla tutorials; the set for the HG Sinanju looks like it touches on a lot of what you're looking for.

Personally I don't have a particular go to place though, most of the time if I have a specific question on like thinning ratios or how to use something I search discord or the first few pages of Google. A lot of like military modeling forums out there where the advice still applies to gunpla, stuff like that.

I started out with a basic harbor freight set; definitely would not recommend. The airbrush is siphon feed so IMO it was a pain to clean, and the compressor didn't come with a tank or regulator.

I bought an Iwata Neo CN a while back, which has been pretty fantastic in comparison. Easy to use, easy to clean. I'm still using the HB compressor because I bought a regulator specifically for it, but I'd definitely recommend just getting one with everything. Regulator is important to be able to control your spray pressure, and the tank will store air and keep your compressor from running all the time. Right now in the hotter months I've been worried about it overheating.

Also if you're spraying indoors a spray booth and respirator are a must, otherwise you're going to be breathing in all those paint fumes.

Good luck with your Aerial! She's a great kit, I was really impressed by the engineering and I'd recommend her to anyone.

I just got back into gunpla after like 9 years not building, here's the HG Aerial I finished a while back. First time airbrushing, was super impressed by the color separation which made it pretty easy to paint.

Also made some trails for the gund bits out of washi tape and wire, might upgrade to those 3D printed ones eventually.