I used to use these cheap little mixers for mixing tattoo inks. The ends are replaceable and cheap on ebay. Could work pretty good for mixing 5ml test batches. Runs on two double a's
I can't remember who the Australian guy is, but I watched a lot of his videos on YouTube before I started DIY - he took the plastic shaft of a q-tip and split one end to make four prongs, put the straight end in a power drill and mixed the crap out of his juices. I'm not that talented, hence the cocktail mixer....lol!