Most of the stuff you will paint will not require much prep, I commonly use brake cleaner to clean the material, let it dry, then apply my coats. That works great on the hard plastic stuff like the dash and center console. The softer plastics like the door arm rests (not the pads) and the rear 1/4 trim peices require some prep work. Those typically need the vinyl primer.
My dash and center console look OEM black, I can clean it with black magic and it shines like new. Holds up well, doesn't chip or fade.
I used Duplicolor and it turned out great. You just really need to prep everything. I took the parts off, cleaned them with soap and water using a brush (you need to get every little bit of dirt out of the cracks)... I also used Acetone (this stuff will melt the plastic if you're not careful).