I used charcoal (the drawerin' kind) and pastels to do this. Taking small pieces of black charcoal and various colors of brown, I crushed them with a hammer in a Ziploc bag until they were a fine powder. Poured them out onto foam picnic plates and rubbed a paper towel into them, dabbing away excess powder, then rubbing into the fabric.
This stuff is so ground in that it won't readily rub off on your fingers, but probably wouldn't stay too well if washed. Fortunately my Fett is a static display and I don't have to worry about him getting sweaty!
After the entire pouch is done I used a tire brush to brush and give an overall smoothness to the filth
This is one weathered pouch (left, duh) next to an un-weathered one. The pouches I made myself using general measurements talked about in different threads on this board. I'll post two different pics each in different lighting.
The second pic, while a tad blurry, is closer to the actual overall color.
Lemme know what you think!