Yup I just have a MAPP/Propane torch and just tried to burn the insides enough to be black, trying to avoid the outside, then sanded it back down.
40, 120, then 240 grit. Might do more but I think it's plenty smooth
Of course!
Hope this link works, check the last few pages for the updated recipe.
https://www.homebrewtalk.com/f12/surly-abrasive-clone-245410/index12.html