When you find a toy soldier (metal or plastic) in decent condition, but badly painted, here's what you can do:

Soak him for at least 12 hours (24-36 hours is preferred) in an old cup filled with FANTASTIC spray cleaner (use full strength). In the morning the paint will slough-off like the skin off an old tomato. I have used this process with success for many years. It works with old Marx, Timpo, Airfix type plastic soldiers and also with Britains and Johillco tin/lead figures. Soaking metal figures for a couple of days will NOT destroy the metal. I've soaked some tin figures for as long as a month and there was no discernable metal oxidation. I just cleaned them with a toothbrush, dried them off, reprimed them, and repainted them. Other friends of mine have used FORMULA 409 and even EASY-OFF OVER CLEANER to strip the tougher paint. They all work pretty much the same. Any industrial strength cleaner should do the job for you.

CAUTION: Beton cowboys, and other acetate based figures will become distorted if left in the solution too long. The soak makes the surface layers peel and the figure comes out kinda shaggy, so unless you are looking to do a 54mm wolfman conversion figure, let the Betons be as you found them. Acetate figures are usually very brittle and distort with age from heat. If you have one of these, don't soak it except, maybe as an experiment.

Always test a new technique with a bad figure first (one you wouldn't mind losing). This soaking process isn't really a trade secret, just something I picked up in my years of collecting. It may save me some work if everybody does it. And CLEAN figures sell better than dirty and badly painted ones anyway. Take care, My Buddies.