From my experience that stuff is pretty terrible no matter how you use it.
Like you, it was the first product I bought when I decided to try sculpting. I did manage to use up my whole supply on a brick wall background which ended up warping over time, but I'll never buy it again.
I switched to Aves Apoxie Fixit Sculpt and so far I couldn't be happier. It's extremely easy to use. A little pricey, maybe, but entirely worth it.