So im working with gumpaste today, this is the satin ice one which has been colored grey with some black americolor coloring.
I had made this on thursday night, and covered it in clingwrap and stored in a ziplock bag in a cupboard.
The problem im having is it seems to be getting to sticky too quickly,
if i try to use to use some cornstarch to "unsicky" it then seems to get too dry and crack.
Am i just using too much corn starch ?
its starting to annoy me now as when im trying to model a shape (figure) it looses it shape because its too sticky or starts to crack because its too dry..

any sugestions welcome...

Thanks

Use a tiny bit of shortening instead. I don't use Satin Ice, I use Nicholas Lodge's gumpaste, but shortening is exactly what it needs to behave better and to give you a slightly longer work time.

Listen to TexasRose, she is very wise. Shortening is your friend with gumpaste, seriously, it makes it behave sooo much better! On your fingers, on your workspace, knead a little in, as Martha would say, "it's a good thing"!

for fondant and gumpaste, I am a firm believer in shortening, not cf or cornstarch

Cornstarch will dry it really fast, I agree. You can add some fondant to try and fix it a little bit. I usually like to work with small pieces, so if it's starts drying I can add more gumpaste and bring it back to life.
Edna