I use browns, tans and some grey. Black is obviously a little harder to show weathering, but these colors pop off of it pretty good.

Use silver on the black parts. that's how i found to do that. Use silver paint or sharpies on a dark helmet

@@TennyDoctor1104 Yup, that is also a great and easy way to add some wear and show the "metallic" base of an item. Just make sure your item is supposed to have a metallic base :)