Although I am only recently getting started with pouring blanks, I started with Alumilite Clear Slow (Urethane resin) and I bought it (and my pressure pot, pigments, dyes, and other stuff) from Exotic Blanks. I chose Alumilite Clear Slow because it has a long enough working time (12 minutes) that I don't need to be in a panic to pour it after I start mixing. It takes me about 5 minutes to mix part A and part B together which leaves about 6 or 7 minutes to get it divided into cups and to stir in the pigments and dyes before I absolutely need to start getting it in the mold.
Alumilite Clear (Urethane) has a 7 minute working time.
Alumilite White (Urethane) only has a 3 minute working time.
Liquid Diamonds (Epoxy Resin) has a very long open time (30-45 minutes).
Alumilite Amazing Clear Cast (Epoxy) about 30 minutes
Alumilite Amazing Deep Pour (Epoxy) about 60 minutes
PTownSubbie has a good video about the different kinds of resins:
Differences in Casting Products.
I have been having a lot of fun since I started casting (only about a month ago).
Regards,
Dave