How long does rattle-can paint really take to dry?

Lae: What is wetsanding? Water and fine wet n dry? Do I use water in between each layer: 2 primer, 2 paint, 2 laquer?

Yes, wetsanding is very fine wetndry paper with water (water with a little drop of washing up liquid is best). You do it on the final topcoat/lacquer to remove the little 'bobbles' of paint that you get from the spray (expensive guns have a better spray pattern so need less sanding... rattlecans give the worst finish so need the most sanding). You need to use a sanding block (a stiff sponge works well because it wraps around the tubes of the bicycle) otherwise you'll get ripples in the paint.

You don't need to wetsand between each layer, but it is a good idea to do so, because it ensures that the paint is flat and has no high spots or low spots (which will show up as little reflections when the topcoat is polished). Wetsanding between coats can be done with something like 800 grit - higher grits are only needed when finishing the topcoat to a high-gloss finish. Be careful not to sand through edges (like lugs) - putting some painter's tape over them when wetsanding the tubes will prevent this.

Some kinds of paint require keying between coats - that is different from wetsanding in that its purpose is to provide a rougher surface onto which the next layer can adhere. Some paints do not require keying between coats so long as the next coat is applied within a set time period (for most cellulose or acrylic rattlecans this period is about half an hour or so).