Yea that shipping is a kick in the ass isn't it!!!
Well i will tell you my experiences.
I did two Romy kits with Krylon BBQ grill paint and it worked fantastic!! Stuff sprayed on perfect, was cheap, dried fast (to handle). I did find that it too seems to take awhile to "cure" or get hard......a solid week if you don't bake it. So i did some testing and baked on 250 for short stints allowing it to heat, cool, heat cool etc...prob 20,30 minute intervals.
I then used the Rustoleum........exact same results as the Krylon. Actually seemed to work a bit nicer on the receiver as it sprayes on as a thinner paint than the krylon. It does not claim to be "heat" resistant so i was hesitant to do the barrel etc with it.....but the receiver no not get over 200 so its fine on that.
Thought, what the hell, lets try the "suggested purpose made" finish. And honestly.......i can't tell the difference. It "may" stick a bit better but thats just a guess from how hard the paint is for me to wash off my fingernails compared to the others. But thats not saying the other finishes don't stick good enough anyhow. My Alumahyde spray looks fantastic.....little more glossy than i would like (semi gloss) but.....its on my AK that is my sort of baby doll one so i don't mind it looking a bit purdy
I would prob say if $$$ isn't an issue buy the matt black Alumahyde II. If $$ is an issue or time or whatever......the others do work just fine and i would not hesitate to use them again. The key is to put the parts in your oven and bake on low to get the paints hard. If you try to assemble even your safety lever or cover when the paint is dry but not cured its going to chip off very easy..........so bake bake bake.