I like to use a buffer because it really saves time. The key with using a buffer and avoiding imperfections is using new or clean polishing/waxing pads whenever you polish and wax your car. Also, when you remove the polish/wax, be sure to use a clean (and soft!!) terry cloth towel or microfiber towel (I prefer microfiber but they are a bit more expensive). When you remove, be sure to take of the wax/polish in a circular motion, and turn the rag over every so often and use a clean section. Also, I always pull the car out into the sun to check that I have removed all of the wax before I proclaim it done, if you miss a spot and let it sit in the sun it will most definetly cause imperfections.
Meguires products are generally considered the best by most people, and no matter what, steer clear of turtle wax. You get what you pay for, and if you go cheap the results will be less than satisfactory. I know DuPont has a new wax out, however I have never used it but I am planning on trying it, it has teflon in it and is supposed to keep contaminents off the paint longer.
Oh, the more coats of polish you put on, the better, the polish is what will give the car a deep wet look, and the wax will protect it.