I think this job called for a drop cloth, if for nothing else,ease of cleanup.
To test for abrasive damage, just clean a small area to see if this is indeed the issue. Don't use water at this point, clean it with a terry cloth and sweep or vacuum it up. Adding water will just turn it back to a slurry. After the dry wipe, see what it looks like. A clean sponge and a single wipe accross the surface will leave it as clean as it's going to get. Dry it and see what you have.