That's a lot of layers of paint.

Don't you worry about it being too thick for the waist articulation? Turning the waist could rub the paint right off the top of the belt.

I do. But I decided to make a compromise with that. I wish I could paint every bit of the belts, but since the top won't be too visible most of the time, I'd just make sure to leave enough clearance for waist rotation.

I also read that the plastic the belts are made of might be soft-vinyl and since vinyl paint exists, that might be another option. But not one I feel too sure of using since I don't know how it might react with the belts.

So I just tried some top coat on a bit of the BAF dino Megazord's skirt armor (made of the same plastic as the belts) and it's not sticky after drying!
So maybe spray on enamel is a viable painting option.