Imho, its the right way to do it, rather trying to cut bits out and patch when the car is complete, parked in a driveway. Can you get repair panels ? What car is it ?
As kid my father had company cars (late 50's / early 60's) so when we visited the dealer for service, repair, new car etc I always used to jump into the one they had in the showroom. I seem to remember that it had a battery so working lights which was amazing compared to the other pedal cars around at the time. When the bonnet was lifted there was a dummy engine.