I've always got by using celotex/kingspan foam to make plugs in the past but I'm now preparing o make my biggest plug yet as body work for a vehicle, its about 2m long and 600mm wide.
Even if I made a wooden structure in the middle to minimise the foam usage, its still going to cost a fortune, so I'd been considering trying polystyrene. I know I can't use any styrene based resins, and the surface detail is going to be terrible so it'll need a skim of filler all over, but can you use 2k paint on polystyrene?
What does everyone else use for large plug making? Are there cheaper foams I could be using?