When you are done coloring, clean off the white areas with clean cotton or the solvent that comes with the set of oils. Finish a fixative, if desired. Let dry overnight. Oil colors can be used to touch up spots on color prints. Oil coloring looks especially nice on sepia toned photographs.
Colored pencil works best on matte surfaces.
Pencils or marking pens can be used to touch up color or black and white photographs, however, some marking pen ink fades with time. Other kinds of ink dry too fast, but you can experiment with solvents such as nail polish remover, which might thin or dissolve the ink. Broad tipped, bright pens will give the print a festive or garish look. Try different kinds of pens on reject prints first. Or, try coloring copy negatives.