Thanks so much for the advice. This is great.
I plan on getting a flat grey and/or white, to spray vehicles & figures with a flat, base color. Then building up colors with some miniature paints like GW, some of my print acrylic inks (they've worked well with plastics and metals, has some thickness to it to build texture if needed, or you can thin them out for weathering/regular painting to do thin, clean layers)- a dull coat, then weathering, then maybe another dull coat (if needed)
I'd rather stay away from black primers, as in the past with some tiles I've painted, it was too hard to get a clean lighter color to "pop" overtop of that.
I've found with tile, which has the same adhesion problems as hasbro plastics, that a flat light grey or flat white, then with a second or third coat of flat white over that, will let colors like yellow orange, the lighter colors, will really "pop"- add glossy paints or finish, and it pops really nicely.
Maybe this approach doesn't work for vehicles or figures? Am I on the right track?
I'm really close to buying one of those Testor's spray sets, am I throwing my money away?