One neat trick I found was using PVA glue and superglue. They react with each other and form a tough wrinkled skin surface. It's nice and organic, making covering large areas much easier than using tones of greenstuff.
And then there is the invaluable instant mould. Heat it up, press onto a surface then run under cool water and save yourself hours of sculpting. Great stuff.
A review has already been done on Chest of colors so I won't cover any more here.