Tell us about yourself!
Using acrylic paint mixes well but it also adds water to the silicone and thus speeds up the curing process (cures faster)
Try InstaMorph thermoplastic pellets. It acts like clay when heated in hot water, but when it cools, it's a strong plastic. It can be shaped by hand when warm or filed, sawed and drilled when cool. More HERE Perhaps plastic bags can be used this way as well but maybe too hot to handle when heated enough to be soft?
I stopped using the Dremel colletts a while a go and use a chuck made for the Dremel that fits every tool shaft I've needed and made the use of my Dremel even more joyful!Walmart has them in my area.
Make a Shrunken Egghead
Drill Press Lathe