Proper Use of the Clay Bar.
Ah yes, that little guy. Before going our and buying an expensive clay bar kit you should first evaluate if you need one or not. How? Glad you asked. After washing your car and drying it place your index finger in a plastic bag and gently run it along the paints surface. If your finger glides effortlessly along a smooth surface then you may skip this step and start waxing. If not keep reading. If you felt tiny bumps and there were parts where your finger had more difficulty advancing then using a clay bar will benefit your surface.
What you'll need.
What clay bar do I get? It depends. Do you want to do this one to two times a year or every month? Clay bars are abrasive by nature. They come in varying degrees. Chose the one that best suits you. If you chose the more coarse one you will only want to use it when necessary or the recommended twice a year. In the early spring and early fall. I chose these two times because they offer the longer time that you will have to benefit from their advantages. By using a clay bar on the vehicle you are riding the surface of contaminants that can damage the paint. Brake dust, acid rain and other contaminants slowly eat away at your paints' finish. The sooner you get rid of them the less damage they can do. By having a smooth surface they will have less to adhere to and will simply fall to the ground or stick to the next car that wasn't properly detailed.
Now that you are ready to start using the clay bar make sure you have enough time to complete the full vehicle as well as applying at least one coat of wax. Being able to store the vehicle indoors will also buy you some time. Don't drive it unprotected though. Start from the top down. Make sure to lubricate the bar well and don't apply too much pressure, let the bar do the work. When the bar starts to get dirty fold it and keep going. Use a micro fiber cloth to keep the area clean and don't allow the lubricating liquid to dry on the surface. Keep going until you've done everything.
Now that you have eliminated the contaminants you are ready to apply the optional fine scratch remover or compound to get rid of swirl marks. If you feel that you won't benefit from that you may apply your favorite wax.