tire weathering?

I like to use pastels ( non-oily ones ), just mix the pastel with alcohol or water into a paste then apply, maybe add a bit on dry powder form, and finnally just for a good touch take your fingure and run it around the sides to get a bit of shine.

Depending on the end result I'm looking for .. I may slap some mud on them but in the end they always get a dusting of pastel chalks. I apply them dry.