[mapsjanhere]

Touching up is iffy since you need to use cold blue, which will not match the color of the factory blue (as you can see by the spots your grandfather's work left). If it's so bad that a refinish is needed and the (real or sentimental) value of the gun supports it (as in it's not so rare that refinishing destroys a huge collector value but valuable enough as a usable gun to justify professional service) I'd have the whole gun hot blued.