First off, if your truck hasn't had any extensive detailing work done to it in a long time it will need more than just a wax. You're going to want to start with a clay bar, then a compound polish, then a machine polish, THEN a couple coats of wax or paint sealant. There's tons of info on all this stuff in the washing and waxing section of the forum HERE
. I'd suggest taking a look through some threads on there. You'll find tons of good information that people have posted. Posts by Primo Spaghetti are always good. He's the waxing and detailing guru on the forum.