Tamiya has 4 different sets of weathering "stuff" each consisting of 3 related colors in a nice little plastic box, along with an applicator. Even comes with an instruction sheet in English.. trouble is, it doesn't work. I could get no powder to transfer from the cakes of "stuff" onto the applicator, nor could I get any of it to stick to the model, even breaking it up and using a fine brush. It is said to be semi-wet, but this was bone dry.
Do you think maybe I got two old sets that were dried out? It looks fine, but it sure doesn't work. Got this at Hobby Lobby. Maybe it was sitting around in a hot warehouse for years.
Anyhow, be careful about buying this stuff. The package is only taped shut, so you could open it in the store and rub one of the cakes and see if anything comes off on your finger. If not, seal it back up and leave it there!
Doc O'Brien's weathering powder, sold by Micro Mark, works great, however. I have a set over 10 years old and I used it yesterday. The 12 little jars will last forever.