About the trim. Take everything off that you can possibly take off, markers etc. To mask all you use is 1/8" masking tape, 3/4" masking tape and masking paper. First sand the car down, dont take down to metal, very bad, paint sticks better to paint. Take the 1/8" masking tape and line everything that you dont want to be painted on, ie trim, windows, headlights, grill, etc, then take the masking paper and the 3/4" tape, line the papers one edge with the tape and apply it to the edge, so its just overlapping the 1/8" tape and cover everything necessary, a razor blade comes in handy for everything. Razor blade is your friend!! Dont be affraid to cut pieces of tape in small chunks, dont try and angle the tape as it will bunch up, clean your car prior to sanding as well, tape doesnt stick very well to dirt, heh. But yah keep the tape fully touching the surface, no lifting or bumps so you have a smooth surface.
To clean off the sanding you can use gunwash, or paint thinner in a spray bottle (if you have one of those pump bottles). First you blow everything off with the air gun then take the gunwash, spray and rub, it takes all the little pieces you missed off. Pretty much clean the car with this stuff as it will leave it looking very dry.
And remember one consistant motion when spraying, keep going at same distance same speed and let go of the trigger before you stop the gun. You wont get runs, drips, light and heavy spots.
Hope this helped yah out.