Hi Harry,
I have used Nitromors, which is a liquid paint stripper, you need a small tray to let the figure sit in till the paint softens, then use a toothbrush to clean it off. pretty messy but very effective though.
I have a few to do myself, and I have been told that a liquid spray oven cleaner is very effective.
here it's called Mr Muscle. I have the product, just haven't tried it yet!!
whatever you use, make sure you wear rubber/ surgical gloves

Nicholas