I've been using SEM paint only, based on reviews that I've seen and positive comparisons to Dupli-color and other rattlecans.
I've been very impressed with SEM, but I can't speak to specific personal experience with other brands.
My 85 GSL interior had been painted by a PO--stereo and shifter bezel, rear compartment plastic trim--and it frankly looked like crap. I don't know if that was due to the paint or the painter, but I did my research to find what was most highly recommended, and it seemed like SEM.
They sell SEM soap, plastic prep and "sand-free" products as well, all of which I purchased and have been using.
I'm converting the interior from grey/dark-grey to black and frankly I've been very pleased with how the plastic trim turned out.
Another thread you should look at is:
The poster there used Dupli-Color products and looks to have had very positive results.
I confess that I adopted the use of the clear dupli-color enamel as a final coat in my efforts as well, and am quite pleased with the results.