You don't need to put your photoflo in the tank. I use a small jug. I take the film off the reel soak it. Then with a gloved pair of fingers I wipe it. Repeat for each roll. If you're only doing two rolls it's not going to take much longer. The little jug I use is big enough to handle anything up to 4x5.

I'm not sure how valid your test for carry over is. Doesn't matter if you can tell if it's there but if it reacts with the next batch of film. Used to be you didn't wash beer glasses with soap because the faint traces that remained in clean glasses would kill the head.