So I ran a couple tests using on older plastics to see about cheaply expanding units.
One is an old plastic Orc from the Warhammer Fantasy Regiments set, the other is a 5th edition Lizardman.
I shaved off the right side of the Orcs chainmail and used Apoxie Sculpt to cover up the rest of the chainmail giving him what I hope looks like a caveman fur tunic and replaced his sword with a sculpted club.
The 'lizardman' had his head replaced and his scales shaved off. Also sculpted a fur cape on his back to cover up the scales.
The lizardmen came out quite well I think.