hmmmm.... :-k
well to be honest..... to save a lot of time, effort and above all money.... i'd be buying a small block of pre-cast resin if its just for a shaving brush handle.
However..... if you do want to give it a go.....
Yes, resin specific pigments (it's been a while, but i'm sure if you tried mixing polyester with an epoxy pigment it wont work.... and vise-versa of course)
Yes.... you can try 'warming' the resin (and if an epoxy system, the hardner component too), i wouldn't go any higher than 35 - 40 c though. The warmed resins will be less viscous and not hang onto the bubbles so easily. But.... it's the tiny little buggers you have to be looking out for.... which is why the vacuum system comes into its own. And bear in mind a 'warmed' resin will cure a darn sight quicker than a cold one.... so you will have far less working time :shock:
You could have a go at making up a Heath-Robinson chamber and try a few samples.... i.e. a bucket with a flat top, a clear plastic 'oversized' lid with a hole in it (read 10" bucket + 12" perspex or similar lid, hole approx 1" dia) and some sort of rubbery gasket between bucket and lid, connect your shop vacuum cleaner to the hole via an optional pipe and switch on. It wont pull a massive vacuum but may just be enough to pull the air bubbles out of a small mixing pot with sample of mixed up resin/hardner in it.... remember, what you're after is a block of resin totally free of even the smallest air pockets.... as pockets = voids = not a good finish achievable without then filling with more resin.... which may have small pockets of air in....... #-o
How do i know...? errrm..... 25+ years working with different resins and different methods of use/application. Most fave is resin infusion......
Nick