I work with two mediums. One is my painting medium that I will mix directly into wet paint and the other is my oiling out medium which is used on a dry paint.
My painting medium is 1 part Black Oil, 1 part Damar Varnish, and 1/2 part Turpentine.
My oiling out medium is 1 part Poppy Oil, 1 part Walnut Oil, 1 part Damar Varnish, and 1/2 part Turpentine.
The description in the video has links where you can find the ingredients.
What mixtures do you use for painting?