A 1/3 too 2/3 mix of Supersculpy Firm and regular supersculpy is supposed to be best,
as when well mixed (with say a pasta machine- which I have yet to acquire one of) it has a beautifully opaque grey surface that really helps to spot imperfections, and hold impressions really well.
The Tar pits section of the clubhouse (link below) is full of dinosaurs, and there are some great tutorials.
oh and good heat gun or blow torch can be invaluable to lock in details without doing a full bake, I use mine sparingly, but tend to do three or four bakes per sculpt.
Trying to train myself to work with as few bakes as possible, but I like to handle a piece as I work it.
so its hard.
as promised here are some good sculpting links.
A friendly forum with some really extraordinary sculptors:
some fun stuff here too
and another more diverse sculpting community here
and of course the sculpting pages of conceptart.org are frankly beyond impressive