I assume they are soft plastic. Not painted many of these in the last few years, though I did do some board gaming pieces for a friend of mine. Did a lot of 15 mm ACW metals about five years ago though, and it’s really only the prep that varies. These are very old figures I think, probably from the 1960s or 1970s. I would clip them into pairs for painting, not take them straight off the sprue. They will be easier to hold like that. Painting them is much easier these days because acrylics are flexible when dry.
Your plan is sound, except I would move step one to after step four so you also remove grease left from clean up and handling when you wash them.
Clean up will involve a very sharp scalpel. Don’t try sanding, they go furry very easily. I’ve heard of some people using a hot paper clip in a holder to smooth edges or even pass them through a candle flame, but I’m not that brave LOL.
During clean up make sure they get a good scrub with dilute washing up liquid to get rid of mould release and surface grease. Paint doesn’t want to stick to polythene, so don't give it any reason not to.
Brush painted acrylic paints and primers are best for these. They are more flexible when dry and will not flake off so readily when pinged. A thicker primer coat may be an advantage for paint adhesion because it is like coating the figure in plastic. Apart from that, I’d paint like anything else. Don’t bother with the eyes, and push the contrast because smaller figures need a bit more to pop. On small stuff like this I tend to block paint, highlight, and then use washes because detail is harder to get looking right at this scale if you paint it on.
Lots out there about painting these on the net.
