"Goo bags - recipe for goo. I've had it suggested to use an entire bottle of dollar store hair gel, but this is probably just as inexpensive, and you can make whatever VIBRANT colours you want." Letter writing with fingers or Q-tips.
AMAZING lava lamp sensory bags. These are easy to make and allow kids to explore in a variety of ways. Learn colors, explore the Science of liquids, create fun works of art, and engage in sensory play in a mess free way. There is no clean up with these and the FUN never ends.