Quite a while back, when the V-22 was a new program, FSM had an article on how to build a scratchbuilt XV-15 demonstrator aircraft.
I wasn't a big fan of the XV-15, but, that "balloon covered wood form for fibreglass fuselage" technique that the builder used lit a fire under me. That article allowed me to go back to "100% plastic" builds again, and still carve masters out of wood. It was also one of those "why didn't I think of that" moments.
The very simple concept is to carve your fuselage in wood, cover it in a balloon, cover the balloon with fibreglass, split that in half to separate it from the wood/balloon, and use that fibreglass as your mold. This allows us to include all the detail on our master that would normally be difficult or impossible to include if we just used the solid wood as our vac-from pattern. Then use Resin, draped hot plastic, more fibreglass, etc to make the part (you could even drill small holes and use it for a vac buck). I believe it also was the first time I saw anyone use microballoons for model building.