Well, without telling you how to go about your painting process in an entirely different manner... I can tell you this. The chipping solution or hairspray (my choice personally) will go down on whatever you want to show underneath what's being chipped away. For example, if it's a metal undersurface you aim to reveal then the hairspray or solution would go on top the metal color. Let's say you wanted some of the zinc chromate color mixed in with this. Put down your metal color, then the zinc chromate color, then your hairspray or what have you. Once it's dried, paint what ever it is you want on top to completion. Whenever you're done, soak the surface in water until it's saturated and slowly pick away until you're happy with the chipping. I personally don't use preshading any more for panel lines especially if I'm chipping the surface, but I don't think you'll have to worry about that too much anyhow. Most of what you'll be seeing is chipping on the panels or along the border. I suppose it depends on how you're going about painting the metal color, but any darker color within the panel lines shouldn't concern you too much. Anything you don't like, you can carefully cover back up with some post shading or weathering depending on your goals.
As for wood or canvas...that's sort of a different monster, but same principal. I paint solely in Tamiya acrylics and in thin coats. The MiG chipping solution did not work out for me too well. The hairspray though hasn't failed me yet...sooooo. Let's say you put down some oil paint in an effort to make a wooden paint scheme that got "painted" over. Same principal...allow the oil to dry, hairspray, then your next color. Use water to soak and chip the appropriate areas, seal in a flat coat or whatever you're looking for and continue whatever weathering you're still need to accomplish. =] It's not too bad.