Jonathan Goodish wrote:
I'm ready to paint my plastic as part of an interior project. I've
painted a couple of pieces with Rustoleum plastic primer, and then with
the appropriate color of gloss enamel.

I know that folks recommend SEM and other vinyl paints. I've also had a
recommendation for Krylon (I assume the enamel similar to Rustoleum.)
How durable is SEM? Is that what I should be using? For the pieces that
I've already painted, can I just paint over them, or do I need to strip
them somehow without trashing the plastic?

A lot depends upon the wear level the part is expected to see. For
things like window trim I've used straight Krylon after cleaning the
part well - works great and still good after 10 years. For high wear
areas (like door trim or panel) the SEM is clearly a stronger bond.

If you are only concerned about the gloss, how about just a light
buffing with a very fine steel wool (and a good wash to remove any
remaining fibers)? Unfortunately, Rustoleum and most other paints
don't like each other. In general, Rustoleum and Krylon will react
rather viciously. You can almost use one as a solvent to remove the
other.

One other thing that I have had recommended, especially on metal parts.
Paint with Krylon, then bake in the kitchen oven for a few days (low
heat). Really hardens the paint and improves the bond. Close to the
baked on enamel we use for commercial panels. Does smell up the
kitchen a bit, and of course on plastic parts one would have to take
great care not to wind up with object d'art. G