Thanks for the advice.

The only reason I mentioned tape is that there's an crack that goes
from the ceiling to a wall and it was repaired before (and recracked).
I was thinking about routing a shallow channel on either side of the
crack with a chisel and setting the fiberglass tape (not the paper
drywall tape) in it so that it wouldn't recrack.

Also, is there any trouble getting finishing plaster to bond with the
top layer of plaster that's already there? I have some small dings,
like something sharp hit the wall and left a divot.

Mike