I tried Citristrip which works on latex and oil-based paint, varnish, lacquer, enamel, polyurethane, shellac, acrylics and epoxy from
wood, metal and masonry surfaces but it did nothing to the green coating on the PCB.

I need to expose the copper leads of a circuit so I can fix the open.

The green coating is typically called "solder mask" - I have not done this myself, but I have seen recommendations for using paint stripper (which, apparently, you tried without success), acetone, or careful application of abrasion, such as with a Dremel, but that risks removing the copper traces too.

It is possible that the solder mask on your board is some kind of epoxy formulation, which would explain the difficulty in stripping it.

I am leaning towards a Dremel (since I have one).

I added a caution above regarding being extra careful with abrasion because it's very easy to go too far and remove the copper traces as well.