[Andrewausfa]

Another method I use is to use the discarded sprues from a model kit, cut them into 1 cm sections, put them in a glass jar and cover them with cellulose thinner. After a day or so they will dissolve into a plastic goop you can fill gaps or mould stuff with (impression moulds). It takes a few days to cure but when ready can be cut and sanded as per styrene. The only thing to watch is slight shrinkage.

Andrew