Here is a sculpting tutorial for gambeson by Eisenhans from over on the Ninth Age forum:

Quote Originally Posted by Eisenhans

Here's a quick n'dirty tutorial for gambeson:
The tools I use:

1.Apply a blob of GS and shape it somewhat into the shape you want.

2.Smooth it.

3.Define the edges by pushing them flat repeatedly.

4.Flatten the top surface.

5.Define the edges again. For a more crisp finish repeat steps 4 and 5 until satisfied.

6. Cut a diagonal line with a blade across the whole surface.

7. Cut a line at the opposite angle.