LD1:
Here's what I do. First do NOT "sand" the case! It's old leather and you'd destroy it. Try to clean off the paint with a solvent: Paint thinner or lacquer thinner used sparingly and with much caution. If some spots remain, try a gentle scraping with a DULL knife. You can't do much about the stains -- but they add character in a way. With the paint off, scrub the exterior with saddle soap. Let dry 24 hrs. Then judge the hue of your leather and get Fiebing's leather dye at a shoe shop -- light or medium brown as you need. Apply this to the WHOLE case, moving quickly and with a modest amount of dye on a folded cloth -- NOT the dauber in the kit. Pay special attention to the chips. Wait 24 hrs. Next, rub in all the Pecard leather prep (in a tub) the surface will absorb -- follow their directions. Polish with a soft cloth and you'll love the result.
Best, Kensal