1. I like to use the liquid liver of sulfur. The liquid solution offers a great deal of consistency and it is easy, just pour it into the bowl and off you go. When I travel, I use the dry chunk form. If you choose to use the dry medium portion out the container into small amounts and store them in a dark airtight container. I use old film canisters.
2. Use of colored pencils, oil based pastels; permanent markers and enamel paints applied to the piece and then sealed offer a wide variety of options.
3. Pigments, spices like paprika, enamel powders, and ground glass can be laid on the piece, layered in Doming Resin or Epoxy to seal them in.
4. The sulphur content in hard-boiled eggs can be used to achieve patinas if you are a very patient person.
I DO NOT use the toxic chemicals like Black Max™ or Silver Black™. Ecologically, they are some of the unfriendliest chemicals around, they smell worse than the Liver of Sulphur ever could. I not so jokingly refer to these chemicals as "Three Headed Baby Chemicals."