WARMAN_316;
This sounds similar to a previous article in FSM. The medium used was (believe it or not) Salt, plain old table salt. The salt crystals are applied with water and a fine brush to pick up individual or multiple crystals/grains. The water temporarily bonds the crystals/grains to the "base" colour that you want to "chip" through to. Then you paint the camouflage scheme or paint scheme you require for your project. When finished you "chip" the paint by removing the salt with either a low-tack tape or with a light scrubbing off with a Scotch-Brite pad. You should be left with a very convincing chipped paint effect.
The salt in two parts acts as 1. A barrier to cover the base coat. 2. As a "template" of sorts to provide random chips, scratched areas.
It is a fairly simple process. I would advise to use a fine grain sand to avoid any salt staining that may arise later. A visit to a local pet store that stocks reptile supplies will provide you with clean fine grain sand in a large amount for next to no cost.
I hope this answers your question.
Cheers;
Gregory