Just got the Z back from a respray...

Spooler

Well, you can do stuff to the paint several days after painting or faster if you have a high end paint booth to bake a car, I would not recommend the average guy touching it. Painting with 2 steps (base coat/clear coat) Most high end shops will wet sand the car with 1500 grit after painting to remove any orange peal or god forbid trash. After that sanding, a professional variable speed buffer is used to polish the paint with grit added to the buffing compound. How much grit? Just enough to get the job done. The next step will be to buff again, polishing away the swirls left from the initial polish. Make a mistake during the process and you will be painting again. As for plastic bumpers. I do not recommend much for them at all. An additional additive is added to these parts to keep the paint from cracking when the panel flexes. It also makes it very very easy to make a mistake when sanding and polishing. The process of wet sanding and polishing new paint freaks most folks out.