Everyone seems to talk about using Rit fabric dyes, but I haven't seen much about the details. I guess just following the directions on the package works. But I figure I should do a little more experimenting, since I want to do this in as little space and time as I can, and because I'm probably working with very small models for the most part. So, a modest experiment with at least a little quantifiable control: pieces from the incorrectly-printed "rattling bones" I ordered a few weeks ago, using Denim Blue, Scarlet, and Golden Yellow dyes, one teaspoon (5ml) of dye powder in 4oz (120ml) of hot water, microwaved (my hot water heater was taking it easy) to get it to around 120-125 degrees F (50Â°C), steeped for about 5min (300s), microwaved a little more to get the temperature up again and then given another five minutes. The results may or may not be well represented by this picture, but were acceptable for me. Not incredibly full-saturation mega-vivid, but definitely colored pretty deeply. The blue looks kind of purplish, and the red especially shows incomplete saturation. But very acceptable, very simple, and it makes details a whole lot easier to see. Have to try some detail material too. May have to go cooler than the directions recommend; detail material isn't very heat-tolerant.