Re: How to Sand Down Concrete Filler ?
Using your example of drywall, the easiest way to do it is to NOT make the mess in the first place.
Cement products are extremely easy to work with while wet, and clean up just as easily as long as you do so while they're wet. When you fill your cracks, clean up the excess before it dries. Smooth the joints before they're dry. Do everything you can during the repair process to NOT make the mess in the first place.
If you must grind on it after the fact, then you're going to need a masonry blade/grinding stone to do so, sand paper isn't going to cut it.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!