AI have a fire helmet cake due this evening and it is complete, except for one thing....she wants it to look "dirty", like it has been through fires, etc. I talked to a cake friend of mine and she suggested cocoa powder, but it didn't really come out like the picture that was given to me for inspiration. Anyone have any suggestions?

This is a link for the cake the customer sent me: http://www.pinterest.com/pin/67835538110549099/ My cake is red, not yellow....

TIA for any help!

That looks like airbrushing to me. If you don't have an airbrush, I believe craft stores sell individual cans of color. Maybe they have black? I've used Wilton brand gold and silver before, but never looked for black.

what about lustre dust or petal powder?

AHershey's special dark cocoa powder is almost black. That might work.