Model aircraft builders use fiberglass and epoxy materials in the construction of their scale airplanes.  This application has challenges for materials and processes, and the video below demonstrates the building of a fuselage for a model airplane.

From Youtube wilmracer

This video outlines the process I used to fabricate the fuselage for my 1/4 scale Pitts Challenger III.

The process involves making a simplified plug and laying the final, airworthy fuselage directly on that plug. This saves considerable time over building a detailed plug and pulling a complex mold from it. There are advantages to that method, but for models that you only want to build 1 or 2 of this alternate method can save you a lot of time.