When the wife ended up with one arm in a cast for weeks I realized what a pain something as simple as putting toothpaste on a brush with one hand was.

I figured that there had to be a simple device that would make it easier.

This is designed for a Colgate toothbrush.  I have included the Fusion360 file so it can be modified for any brand. I also included a shorter version.  She prefers the longer version.