Actually, I just got my weathered BobaMaker soft goods yesterday (he does incedible work BTW) which he weathered with brown paints as mentioned above. I wanted a slightly different, darker look, along with the "waded in a swamp look", so I misted flat black spray paint here and there on top of what he did.
The weathering doesn't show up as well in the pix, but this is what it ended up looking like (forgive the pose -- this is very much a work in progress):

I'm 99.9% satisfied. I might hit the bottoms with a little more paint later on.
What Lynn did with the dye just rocks though.
Cheers!
TJ