Making parts using composite materials such as Fibreglass, Carbon Fibre or Kevlar usually requires the use of a mould. The mould serves 2 main purposes. The firstly to replicate the desired shape of the part and the second being to reproduce a high quality surface finish. Manufacturing moulds directly or moulds produced from plugs lends itself to cnc machining techniques.
Here is a set of plugs that have been machined from MDF soaked in thin epoxy. 
These will now be sanded smooth to carefully remove any machine marks, sealed and sanded again, then polished and waxed to a mirror shine. A standard GRP mould is then produced by laying up tooling gelcoat/glass&epoxy/poraver/glass&epoxy. Once the mould has cured it is then puuled from the plug. The mould surface is then polished and waxed ready for laying up composite parts.
These will now be sanded smooth to carefully remove any machine marks, sealed and sanded again, then polished and waxed to a mirror shine. A standard GRP mould is then produced by laying up tooling gelcoat/glass&epoxy/poraver/glass&epoxy. Once the mould has cured it is then puuled from the plug. The mould surface is then polished and waxed ready for laying up composite parts.