I started with some knockoff clear shells and used this plus this for mister chef's but I think I used too much black. For barbieter, I used this and it was way more pink once done than I wanted. It probably could have used some black or blue added.
Both color sets were put in my heated ultrasonic cleaner at 50c for 20 minutes then removed, washed in cold water and allowed to dry. Heads up, the dye packets come with an intensifier, I used it on both but it has a weird chemical smell that lingers after you take and wash the parts. About a week on, they don't stink anymore.
The shells themselves were mid quality. The d-pads are super sloppy and the buttons stick so I used the original buttons from the first party shells. The gold shell I bought for the green accents needed the shoulder buttons and select button adjusted, it also came with 2 left triggers... Overall, I like how they came out. I wish the green was lighter but thats my fault. I may do some backlights or something in them to accent it but for now, its a unique setup and not sticky with 20 years of Doritos powder and baja blast.
The rit synthetic fabric dye works on some plastics as well. I originally got that to use on my gamecube controller port cover and figured why not try it here. I did the purple one first, and when it turned out more pink colored I tried adding the black since I wanted a more olive green color.
The ultrasonic cleaner was just because it had the ability to heat the fluid inside and maintain the temperature rather than boiling and letting it cool down. I am curious if running the ultrasonics would have made a difference in how well the dye was mixed but I didn't test that.
I don't have any additional resources, I learned about this stuff on youtube from a guy who was doing a wii shell. I'll see if I can find the link.