Magnetic Slime--really neat, but it requires liquid starch, iron oxide powder, and really strong neodymium magnets. There is a commercially available magnet putty that might be a good substitute for exploration.
Jim Snitily 2200 F Cone 5 - I brushed three coats in different directions of the black ( also added 2% black iron oxide to the base) Then applied 2-3 coats of the crawl with 4 inch wide brush medium thick, just so it goes on smooth, not runny. When that dries, it will crack and that shows its thick enough
*Sharon Skelter - Using a variety of hand building techniques such as hollow form slab and coil building, along with heavily textured surfaces builds interest in the work. The pieces are then finished with iron oxide washes and colored glazes.