Andy,
1) I use what is left over from other projects, preferably low viscosity. I coat the raw wood with straight mixed epoxy first, and then put the wood flour filled "puddy" on. FWIW, my resin preferences are low viscosity and non-blushing, so the brands I've used are System 3, MAS, RAKA and 1 other a can't remember at this time. I've never tried West.
2) Yes, either the purchased stuff or collect it from your sawdust pile (but take only the very fine dust)
Dan