I think you might be better off with white metal casting for these guys. Resin would be very brittle , plus you would need a Vacuum/Pressure setup to get the best out of resin.
While you can get very fine details with a gravity cast in white metal, spin casting would be your best bet. I first got into casting with white metal and some of the parts wee very fine, venting and having a warm mould to pour into were key.
The other good thing about white metal, is there is no wastage. Any miscasts damages and cut off sprues are re-used.
I would really recommend watching this video on youtube, very informative.https://www.youtube.com/watch?v=IYVIVzCmH10