weathering methods used?

just looking to see what kind of methods are out there for weathering jango armor and helmets...ive got the r&b done on most parts and need to think about a good method to weather them now...i know most if not all the weathering is shades of black

So far for weathering I use the drybrush and lightly damp paper napkin technique using acrylics. I Get the look I want with the two and wait till its semi dry and scuff it up with my finger nails. I think that does the job for a good dirty look. But would love to here other techniques since I'm just a rookie at this sort of thing.