Double Exposure: 2 photographers on 1 roll of film

I recently bought a old camera from a charity shop its meant to take 120 film I've been putting normal 35mm film though, I've re discovered my love of double exposures.

I am actually going to have to buy a new old camera for this swap, (one that doesn't create doubles).(have got new old camera now, testing it.)

Each person will expose a roll of 35mm film and manually wind it back but not quite all the way so they can send it to their partner for them to use again.