Use Gamblin Solvent Free fluid for your basic medium, and use Safflower Oil for painting and cleaning your brush.
Safflower Oil can also be use as a slow drying painting medium.
Some students use walnut oil as their medium.
The drawback of the completely solvent free painting is that solvent free mediums and fluids are “100%” fat. Which means they produce layers that are more inclined to wrinkling.
Also, it is difficult to produce the best glazes with fat mediums. The best glazes require about 50% medium to 50% Gamsol.
The drawbacks are often not a concern to the dedicated non-toxic solvent free painters.