I've done a couple of re-paints for freinds, and never found them to be too bendy.
Some don't even need to be stripped, just over painted.
When it comes to stripping the paint, nail polish remover is best - but you will find it makes the vinyl "bendy" untill its totally dry/evaporated.
Leave it for 24 hours or so, then clean up with a sharp knife.
Re-Assemble (if required, it generally is) and use a good quality undercoat - they soon "stiffen up" again.
Base and Paint as normal.
I'm trying to collect a decent lineup of the Golden Age Justice Society (without paying the earth LoL) so far I have Hawkman, Green Lantern, and Doctor Fate.
Ebay is your friend with these things LoL!