There's also a route using that
Blue Stuff moulding material which allows you to make a mould from a master (it's thermoplastic, so just needs heating in water- and can be re-used). You can than simply press a suitable modelling putty into it. Probably not very good for the final finish, but OK to produce the basic forms.
I'm not sure whether this would be considered piracy/re-casting, but you could also use it to reproduce faces from a master (ie another model) which can then be re-shaped to create a unique character.
There's
plenty of videos online about doing this... though some verge a little too close to actual piracy.
Here's some I experimented with: the armour is taken from my MM Mounted Samurai (just as an experiment), the other items are moulded from my scratchbuilt 1/12th samurai (now almost 50 years into the build and no further on
)
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