Maybe for collecting and preparing the medium. Maybe all the guns are for training/classes.

@BeeHappy From the film collecting was by hand on the street into a garbage bag. Preparation looked like it required a pair of shears or scissors to cut the plastic film into strips. No, I think the heat guns were only used in application. If he had done all the work alone and from the quantity in the gallery there were many months if not years of production on display.

@BeeHappy Could be dueling hot air at dawn at one pace??

That too! Lol