This simple stirring stick prints flat and connects to any standard handheld drill (1cm hex bit). I used it for dissolving salt in vinegar (and a bit of dish soap) for a natural weed killer but it should work for mixing paint as well. Spin clockwise for a downward mixing force or vice-versa.

I printed the 400mm version solid with ASA so it can handle some flexing. I imagine PLA or PETG could work with the shorter lengths. The standard mixer is 38mm wide to fit in the top of my pressure sprayer, but I've included 68mm wide versions as well, which can be more effective when that isn't a constraint.

Print includes a small foot at the drill end for bed adhesion since long narrow parts in ASA/ABS tend to shrink and warp. You can slice it off after printing with an x-acto/utility knife. You may want to add an additional brim as well depending on how good your bed adhesion is.

Photographed model was printed using QIDI ASA Green (Amazon) on the Qidi Plus4 3D Printer (Also on Amazon).