Most of the nuts came out with minimal force, but the last one just spins in place. I tried rubber gloves, painter's tape, and duct tape to get a better grip. I'd rather not cut a slot in the domed nut if there's another good strategy.
The rest of the restoration underway:
Living in salt country, I've found heat and percussion to be helpful. Hold a soldering iron to the nut for 3-5 minutes, then wail on it with a rubber mallet. Repeat a few times if needed. Usually loosens up the fastener because it dislodges the gunk in the threads.
this for sure first. least destructive and most likely to do anything