the nicest stuff to use to fill voids in glassed surfaces etc, is evercoat, you get it at auto paint stores, dont bother looking in walmart, etc. for it. It is really smooth stuff, much nicer than bondo and way more body than that red glaze stuff. The only down sides are it smells bad and you have to use laquer thinner to clean up tools. it comes with a catalyst, about $10.00 for a can If I recall. This stuff was mentioned in RCR, march edition, they liked it too.

Peter