I tried painting a belt using a mesh tangerine bag as the scale stencil. That was fail.

I ordered a laundry bag online. Perfect! It really did the trick making realistic scales. I used spray adhesive to hold it to the belt and when I pulled it off, paint came with it.

None of the vids I've watched have any advice on that. Does anyone here?

It wasn't a heavy spray, just enough to tack it to the belt. This would have turned out well except for the paint peeling off. I didn't use a top coat so maybe I can scrub it off and try again with the Createx.
You should have use clips or clothes pegs on the back to keep it tight.

I did! I used clothes pins down both sides to hold the mesh in place, but I also sprayed it with the adhesive because a guy on a video said to. :)

It's the snakeskin video where he paints a rifle. It is so good, if you set that rifle down in the weeds you'd never find it again.
Maybe the adhesive isn't behaving on leather (if it's a leather belt :) ) the same way as it does on the rifle, or maybe the glue you have is a bit stronger or the nozzle may lay a heavier coat ??? Hard to say I guess. But it might be the paiant, what paint did you use?

I've seen the vid i think, and if it's the same one, there were bottles of auto air in the background, my experience of auto air (which isn't much to be honest, I never really used it after a few tries, as I din't like it) is that it took a while to dry, and seemed to stay tacky for a while. Staying wetter longer might help when taking off the netting as if totally dry the edges of the net and the paint will have bonded a bit and so removing the net could lift the paint too. That's the only thing that I can think of, unless the netting is sticking too well to the adhesive, and as you lift it, it is moving the paint on top of it causing it to crack off maybe.
Also, the problem with leather is that it needs to be super clean. All the polishes and oils and stuff can affect adhesion of paint.