I use a program written by a man named Phil Harvey to add EXIF info to my scanned film files. It doesn't come with its own GUI though, so I've been using it from the command line.
I got off my duff and wrote a GUI interface for it. It lets me add cameras, makes, models and apply the data to a directory full of scanned jpg files. If anyone would like to use it, you may download it at:
Note, it won't work at all if you haven't downloaded Phil's great tool. Instructions are linked on the program's main screen.