Well I was using Mig's acrylic paint to paint one part, a part for the Churchill, the air intake stack.
So put the paint on ,same paint that I used on the model.
But no primer as I figured,well will not be getting an serious weathering, I waited about 5 hours . I used Mig's Brown panel wash to accent some pieces on it,while using a mild Mineral spirits , to clean some areas, the paint started to lift in some areas not bad but straight down to the plastic.Actually worked out good for applying rust spots, but the question anybody else have that problem with Mig paints, I have put Oil washes over Lifecolor and Vallejo with no problem, no coat of flat first.

First time I have painted using Mig paints, and the first time without any sealer,mostly I use Tamiya to paint stuff, no problem there.

I have had the same issue with Ammo by Mig paint, I coat with Future first before applying any enamels. I usually only do panel lines and pin washes. I then apply an acrylic flat coat, then do the rest of the weathering.