pipe thread compound
Thanks for helpful advice. As you might imagine, we try to keep our own schedule as to when house items get replaced. If we're not sure we want to keep that sink then we'd hate to throw good money after bad and go through buying a new faucet. Of course fixtures etc. don't always age according to our schedule, but I try to find the simplest solution.
In this case I was able to re-install the aerator by using the pipe thread compound--working for now at least with no leak. The mistake I made, was first, not fully cleaning out the corrosion from the female threads of the spout, and second, trying to use a vise grip--even lightly-- to tighten the aerator, even though I knew better. If you don't do this often enough you forget. Best thing is to tighten it only by hand, using a cloth for extra traction if needed.
But thanks for the tip on the basin wrench--good to have these things handy for simple jobs. Plumbers in my area cost a fortune. Thanks.