Here's a quick review of the new Liquid Green Stuff Games Workshop is offering. Readers digest version:
Easy to apply with a paint brush.
Super handy that its water soluble (easy to clean up, and smooth out).
Easy to sand or scrape after dry.
Dries relatively quickly.
Some shrinkage after it drys
GW's paint container... not sure how long before it dries out.
And here's the video showing it in action: