Milliput is a range of 2 part epoxies which have long been the staple of many hobbyists, retaining many of the helpful characteristics of clay once mixed it can be used for a multitude of sculpting and modelling applications.
Milliput standard is great for building texture on bases, all can be used for sculpting, Superfine White is the finest of the ranes available, if you are doing particularly detailed work. In comparison to traditional sculpting materials (green stuff) once dried it is sandable, and can be scraped and filed to shape.
Milliput can be mixed (in varying proportions) with Green Stuff Epoxy in order to borrow the best properties of the two differing materials.