Drywall ceiling with sand finish was stained along a joint from a leak. Leak has been repaired. I'd like to replace the tape, where necessary, and match the sand finish as closely as possible. I've done drywall repair successfully, but only on smooth walls. Will it be possible to (carefully) scrape off the old sand finish by softening it with water and using a taping knife, rather than sanding it? (The ceiling has been painted a couple of times over the years.) Does the sand go into the last layer of compound, the primer, or the paint itself? I'm figuring I'll need to sand between all procedures.