One material I tend to use is a putty called Modeling Paste, made by
Liquitex. It is used in acrylic painting as a thickener, or as a means
of building up a painting and facilitating texture. It's consitency is
that of a sort of thick peanut butter, and it comes in a default white
color, though it can aslo be mixed with acrylic paint in order to color
it. Once dry, it is very strong, and can be sanded to a very smooth
consitency. You can find it in just about any art supply or craft store.
If you have any less-than-favorite incomplete projects, it might be
worth picking up a small jar just to experiment with. Even if it
doesn't meet your needs on the model itself, it definitely will work
nicely for creating terrain effects.
![Smile [:)]](/FSM/CS/emoticons/icon_smile.gif)