When I post anything about painting enamel over acrylic I usually quote the party line stating enamel over acrylic is usually a bad idea. I normally try and add that I haven't tried it myself and that many people have told me that it can be done without problems. I tried it myself today.
The Blackbox cockpit for my F-105G has a "Tub" with some of the side instrument panels molded into the tub. The basic color for the cockpit is gray, but those side instrument panels have to be black. I airbrushed the entire tub gray last Sunday and added a coat of Future. Monday I noticed a few cracks in the gray, apparently I didn't wait long enough before spraying the Future so I sprayed it gray again. This time I didn't add another Future coat because I didn't want to fill in the detail too much.
I've stalled all week trying to figure out a good way to paint those side instrument panels, tried masking them a couple of times and didn't feel like it was accurate enough. This morning I decided that right or wrong I was going to hand brush flat black over the gray acrylic (I've had enough of trying to brush ANYTHING over flat black acrylic so I always use flat black enamel).
I thinned the enamel pretty thin with mineral spirits so it wouldn't block up the detail too badly, got out a nice soft brush, and painted the side panels. Guess what? No problems at all. The enamel didn't dissolve the acrylic, no brush marks, no problems at all. It hasn't cured completely yet, but it's dry to the touch.
All you guys who told me that enamel over acrylic would work were right and my inclination was wrong!
The knowledge available on this forum never ceases to amaze me.