Use the sharp end of a screwdriver or putty knife to chip away at the paint. Be cautious so as not to permanently damage the screw head. If you don't mind damaging the hinges, use a wire brush.
If the paint is too thick to reach with either tool, apply solvent very lightly to the paint. The paint solvent will dissolve most paint.
Use a knife to slice through the paint accumulated between the screw head and the surface. If this seal is not broken, the screw will remain stuck to the surface.
With the paint broken, you can use an everyday screwdriver to manually remove the screw. Using an electric screwdriver might damage the paint around the screw head.