Dry Brushing Using Ordinary Paper

You read that right! Ok, so here's a really simple way of doing weathering on your model kit. I sprayed on silver (industrial spray paint) on plain paper, let it dry, then cut a small piece.
Rubbed the painted side on the tracks of this kit (border break heavy guard).
The tracks are painted graphite black, the bottom one is the one rubbed with silver paint on paper. It's easy to erase if you overdo it. It's just like chalk, just use q-tip dipped in plain water. Seal with top coat or clear coat when you have achieved the desired effect. Careful not to put your finger print on the weathered areas.

*may not work with all types of paint. only those with "powdery residue" like flats, or in this case, silver.