I don't think the hand cleaner is a good idea, (citric acid?) it will most likely eat limestone . If you do find a solvent (acetone (nail polish remover)) you need to get it out while the paint is still in solution, a poultice perhaps, otherwise in can reapply in the stone and be worse than before. Be careful of test areas done under one environmental condition and full scale work done under different circumstances. Keep better records of all testing than you can possibly need and you might end up with barely enough information to make a good choice. Creighton