clear over poly

hello guys thanks to everyone that helps out.I painted my truck bout 6 months back an 4 my first paint job it looks pretty good................but i been thinkin bout puttin a clear coat on it now because its almost like dirt an polluntants are gettin into my paint and i have to frequently wash and wax to keep it lookin clean and somewhat shiny.keep in mind im not a painter by no means just like working in my shop.when i painted the truck i used emrom urathane paint .what kind of clear should i purchase and what steps do i take before,during applying this clear to avoid some of the problems that i have read on this forum such as fish eyes,cracking and what all.also can pearl be applied in the clear coat or just the color coat because i have alittle an my wife realy likes that looks.thanks for replies