You will need:
Testors Modeling Paint
EZ Digital Caliper (only if you don't use my measurements or want to teach the tool)
Pre-made Lego bodies to test
Here is my project to copy and tinker. The hole inside the orange cylinder is the one that needs to be exact. It is 5.5mm X 5.05mm. All other measurements and shapes can be played with to make huge "Bobble-head" like Lego heads. You can easily delete the hat and ears if you want a standard Lego head or get funkier.
After the meticulousness of painting such a small item as well as the nit-picky measurements, I'd advise middle-high school students for this project. Larger heads might lower the grade level.
The print is made all in one piece with the hat and ears not being removable. I used Testors modeling paint to customize which only required one coat and a sharpie for the facial features.
The print was only 18 minutes, no supports necessary.