The red gizmo that is supplied with Jobo reels is intended for that : lift the gizmo, load the first film till the end of the reel (I tend to "screw" it by holding the film in one hand and turning the reel in the other) then close the gizmo, load the second film...

Some people use the tape at the end of the first film to "couple" the films together, I've nevcer tried it.

I had only one failure with my method, where two TXP ovelapped and I lost a few frames, but it is usually working fine.