I really dislike babysitting paint mixing, so I made this caddy to hold up to three paints while I paint or model.
The sleeves are to provide better fitment for smaller droppers from Vallejo/Army Painter/etc…
The main body and sleeves have a few strips of self-adhesive felt liner to provide a friction fit and keep paints from shaking out of the mixer at full speed. It helps quiet it down significantly too. This is what I used for the felt (link goes to amazon).