try the leader card tape that minilabs use to attach film to the leader cards in the Roller transport processors. It doesn't flake or break down with chemistry or higher temperatures, like standard tape would/could

see here for it

I use the 1/2", cut a strip about the length of the width of the film( about 2.5" or so, and tape it to the wall where near I load. load roll #1 almost, with about 2-3" of film left hanging out. unwrap roll #2, detach film COMPLETELY from paper backing, have film curled up in hand, and then proceed to tape the rolls but ends together, and tape.

takes a bit to get it, and a few trys and a few expletives later :P, I finally got it. now its less than 30s or so to get it down. NO red clips, no fuss.

just be careful about which developer you use, and with smaller(weaker) dilutions of developer, cause you will most likely have to use a stronger dilution that with 1 roll of 120, due to 2x the sq. footage of film in the tank.