A toothpick swirl is a simple method for incorporating tiny amounts of very potent essential oils into projects—essential oils like vetiver, cade, or birch tar, which are so strong that even a single drop can completely overpower a lotion or salve recipe.
To measure out a toothpick swirl (which is not at all a reliable measurement and is just a simple way to incorporate a minuscule amount of an essential oil in a small batch of something), you’ll need a toothpick that isn’t minty flavoured.
Simply dip the tip of that toothpick into your essential oil, and then stir your lotion/liquid oils/etc. with that toothpick. The deeper you dip the toothpick, the more essential oil you’ll get and the stronger the scent will be. I recommend starting with what seems like too little and working your way up (use the clean end of the toothpick for your second dip, and a second toothpick if you need to do a third dip) since it’s much easier to add more than to take some out!