Epoxy Putty 101

I have been building for a while, (a couple of years), and have decided to use putty on a couple projects.  Now I've heard about epoxy putty, but haven't seen a whole lot of articles on its use, recommendations on brands, or techniques.  My first application for it would be figure conversions as a filler and to construct packs and the like for figures.  I can use all the help I can get, so any information is welcome.  My main question though is brands and warnings about past mishaps.  Thanks in advance!