As far as paint removal, I can't help with that. But I just painted my engine cover and pretty much did the same exact order of instructions Blue10CamaroSS has listed with a few minor differences. I didn't sand anything. I thought about it, but my dad suggested that I not do it since it was plastic. The primer I used was an adhesion promotor. I've been told it is different than a standard primer and better for plastic. I bought it at Autozone. However, Blue10's turned out great so it looks like his primer worked well too. Not sure if you used a spray gun trigger, but I did, and it was totally worth the extra $4 for it. I am not a professional painter (nor do I play on TV LOL). But the ease of spraying and the control I had with the trigger made a HUGE difference for me. Also remember that when you begin to spray, begin spraying just to the side of the cover, not directly over it. And when you end spraying, end past the cover, not directly over it. This will prevent any type of spattering that may occur when you release the trigger. Especially if you aren't using the trigger gun. http://www.automotivetouchup.com/sto...l_trigger.aspx
All of my color matched paint and clearcoat came from automotive touchup as well.
Hope this helps and good luck.