I've long been on a quest to reduce my exposure to toxic ingredients in art materials I use in the studio. After donning vinyl gloves, the next step of my morning ritual is massaging a bit of walnut oil into my brushes. It not only keeps the bristles nice and pliable but also creates a barrier to getting paint imbedded deep in the bristles.
The most recent miracle substance I've discovered, however, is spike oil of lavender. It's nothing new to the old masters of painting--just new to me these past two years. Lavender oil is wonderful for brushing your first veil of paint on a canvas. The volatile oils evaporate quickly, leaving a wonderfully receptive surface that grabs a brushstroke, while also providing enough emollient film to allow the paint to glide. It's a sensual pleasure, and in a solitary studio, I savor these small pleasures.
Spike oil of lavender may also be used to clean brushes, but to a working artist like me, it comes at too dear a price for such uses. For that, I work out the day's paint with Goop, a waterless hand cleaner I get at the auto parts store. Don't get the kind with pumice, though--that's hard on expensive brushes.
Besides the initial sweep of lavender to tone my canvas, I like to make a medium of one-third parts of walnut oil to two-thirds lavender. When I need a quicker drying paint, I add some Griffin Alkyd White to my paint mixture and a dot of this medium. For a longer drying window, use your regular white of choice to the medium.
Here's a link to my favorite supplier and some commentary from other artists: