Some colours react differently to individual waxes. Silvers work better with sealants rather than waxes, giving a glossy finish. High pigment colours like blacks and reds are better with waxes IMHO. Some great suggestions up there, the meguiars 3 step is time consuming and gives ok results, Nxt Gen wax doesn't last long at all. Any of the Dodo juices are great, Autoglym HD has got everyone raving and is available easily. Collinite lasts ages and gives good results, I use Finish Kare 1000p sealant on my silver A3, i can then use a wax on top of that if I wish but there's no need. As said at the top, Preparation is the key. cleanyourcar.co.uk is a good starting place. All the guides you'll need on the forum there!!! Wash, De-tar, clay, polish, seal, wax should see you right, but it can take all day!!! Let us know how you get on mate!