Field strip it.
Remove the grips.
Get a can of carb cleaner or brake cleaner.
Wear safety glasses/goggles and rubber gloves and spray that thing down good inside and outside (while you're outside) with the carb or brake cleaner. Keep spraying till the crud stops running out. Use the little tube that is taped to the can to reach back in the cracks/crevices and blow that old dirt/oil/crud out of there.
Let it dry, spray with some kind of spray oil/lube to keep the bare metal from rusting (the carb/brake cleaner may remove the rest of that old paint, too. It also removes the protective/lubricating oil from the metal surfaces and it'll rust quick if you don't get some oil back on it. Spray oil of some kind will let you work it back in places you can't wipe it on/into. Wipe off the excess oil/lube as it runs out.
Then you'll be ready to inspect the parts once they're good and clean.
Lots of folks will probably speak up about recommendations for replacing springs, etc. You can either try it as is to see how it works or just take it on faith that lots of use/firing and lots of years will make spring replacement a good thing.
You may find the cleaning, inspection, selection of new parts, installation of new parts, and "tuning" it up lots of fun. Hope so. I did when I got my "ugly" Pre CZ 85 a couple years ago.