Don't try walnut, cherry, cedar, osage orange, or magnolia. Also don't try to spalt dry wood. How do you know when the spalting is optimum. Darrell takes a piece every once and a while and tests it by turning a piece. The length of the log also determines the length of time to spalt.
Red maple is the fastest with the harder woods slower.
Set the screws, remove them, then use super glue to solidify screw holes. You get a very pithy surface and pull out fibers when you turn the spalted wood so he sands. Inside he starts with 36 grit and progresses to finer grades. Since spalted wood contains various hardnesses of material, you should sand lightly. You can use super glue to protect various parts of a turning so that the sand paper doesn't dig in.