david weaver
3. I would depend on something else for the coarser grits, unless you have something to power the MDF. You could stick PSA sandpaper to something, or use some mild steel or cast iron and use diamonds at the 1000/2000 grit level.

Autosol or chromium oxide powder/paste/stick is fine to use on MDF. Autosol will make a pretty fine edge, but it does leave a film of black stuff on a tool.