A clay that I’ve had very little chance to try is resin clay. There’s a few brands out there and they mostly seem to work like air drying clay, curing at room temperature over a period of time.
The bangle project – a sample for Sheri Haab’s resin clay book – uses a former or armature for the bangle and nice colouring pencils to do the graffiti after the clay has cured. Sanding is like polymer clay sanding: wet sanding is safer.
If resin clay interests you, you should check out the book. Sheri Haab has many, many craft books to enjoy.