So the color is not important. Main features are that it is hard, has fine details, sandable/polishable and during casting "air facing surface" solidify to an almost mirror finish. I know many of these features are relative but still with your experience you may have an idea what I can use.
If anyone has an idea please let me know. Since I have easy access to Smooth-on line, if you may happen to suggest a product from their lineup, it will be much appreciated.