Just had a thought... you could make in-camera separation negs w/ panchro 4x5" and then you could use ortho for the enlarging process. Granted, you'd be introducing another optical step and thus a loss of resolution, but since it's for a gum print I'm guessing you wouldn't notice. Might simplify things?
There are some very nice tri-color cameras that are or were available on EBay and other sites. Some of the guys on the yahoo dye transfer forum use these cameras for the original image and do as said by Holmburgers.
You cannot use CC filters for making separations, as the CC filters never reach the cutoff value that true Wratten separation filters do.