My housemate was going on a trip to Alaska the next morning. She had a mostly empty 3 oz toothpaste tube and she was trying to refill it from a larger tube. No idea what she was so opposed to just buying toothpaste when she arrived. I think she was mostly just doing it because she could.

The solution involved holding the tubes end to end and squeezing the larger tube, alternating with using a stirring rod to pack the toothpaste into the smaller tube.