A booth will not guarantee no dirt in the paint. There will always be something in the paint, that's what a wet sand and buff is for. As some have said here, I like to avoid any tape lines in the jambs so on solid colors (non metallics) I will spray all pieces separate. With a metallic, I jamb it, put it together, spray color then take it apart to clear it. It's alot of work any way you do it. Good luck and post some pics of the car!