Basic hobby resin is cheap, you get what you pay for. Its surface texture is wonky, air bubbles can lurk just below the surface and leaching can be an issue. Its cheap for a reason.
If you want to do it and do it right, use a better material. I use MPK90 high impact. Never an issue when using it, never, and ive been with it from day one of its inception.
http://hobbysilicone.com/resins/#mpk90blk
As for the surface finish, if you use the above black color MPK90, simply coat your mould with graphite powder and pour away. As always for moulding and casting, every step is all about prep. Thats how I can cast in color parts, its all prep. But the basics is where to start. Casting in (multiple) color is a niche market for me thats brought lots of work so I wont be doing any tutorials or such. It couldnt even be explained in type form. Ive even had a close friend that knows industry moulding and casting work with me side by side trying to learn it that couldnt comprehend the process.
Graphite powder was the base here but there is more layered in than just the graphite. As a base though, its your best bang for the buck. Again black MPK90 casting material was used. Cheap hobby store resin will not yield the same or even similar results. The detail on the revolver cylinders wouldnt come out in cheap resin.
The real one is bottom right, castings are middle top and left.
Real one top left, again all have zero paint, strait from the mould.
More gun parts, strait form the mould:
and those untouched parts assembled:
the whole casting put together along with cast in color grips.
it works with knives too, strait from the mould as evident by the pour sprues.
