With poor patterns or no patterns at all, it makes the job a trial and fit game. The sheet metal is part of the fit so it has to be involved to get good fit and finish of everything.
Where you have no patterns or not so good ones. A person can use soft foam like the formaldehyde based stuff to rough out pieces to get a fit. This will at least give a person a pattern to work with. It may not be a perfect one but who cares as long as it gives a good fit to the metal parts and your doors will close and pretty much stay that way. Someone is bound to have done a 1924 Touring out there. The clubs are also good places to check. Ford Wood prices pieces separately but I can't vouch for fit since I haven't used their pieces.
https://fordwood.com/images/tour23new.jpg