I am a big advocate of not compromising health for art's sake, simply because there is no need to. As a matter of fact, aside from the serious health reasons, there is need NOT to use turps or mineral spirits in the foundation of an oil painting.
There is all this mystique around the cutting in of turpentine or mineral spirits with your oil paints and mediums to first prime and then build the foundation for a painting. Artists do this not because there is any benefit or logic to it, but simply because it has been done that way before.
Think about it. Turps and mineral spirits are solvents. When building the bottom structure of anything, do you want something that erodes? It would be like building a foundation of a house with blocks, battery acid and no mortar.
Google about cutting in solvents; warnings are everywhere about damaging the binding quality of the paint and mediums. You are ruining the structural integrity of your painting and risking adhesion failure at the very bottom, between the gessoed canvas and the paint. Some advocates of turps will tout “fat over lean” (“fat refers to oil content). Turps in the mix will certainly make your paint “leaner”, but not the kind of “lean” that you want. A very thin coat of oil binder or paint (paint has a oil binder within it already) will initially add to adhesion of paint to a canvas. This is the "lean" that you want! However, once it gets to the point where the oil or the diluted oily paint is applied more thickly, it will pool up, create a really shiny surface and lose its “tooth” (ability to attach to something else). It now resists adhesion – above and below. What you want is the tight adhesion in the foundational layers that a thinly applied, SMALL amount of oil gives – thus the adage: “Fat over lean”. Any oiliness should be reserved for the very last, when you don’t have to worry about things sticking to your surface anymore. What you DON’T want is LACK of adhesion. That is what solvents create in the foundational layers or in any layers, for that matter. This kind of “lean” is exceeding bad for both your painting and you.
My advice: For colour priming, cut to as low a pigmentation as you wish, using either a completely non-toxic cold-pressed linseed oil like Williamburg, Graham’s Walnut Oil, or my hands-down favourite: Graham’s Walnut Alkyd Medium. Then, using a rag or a very stiff brush create a high paint-spread by using lots of “elbow grease” – that is, PUSH the blend of binding medium and paint so that you achieve a sheen, NOT a shine. This will give you any dilution of pigment that you want and still keep an excellent adhesion to your gessoed canvas. When blocking an under-painting either on this or a fresh gessoed canvas, use the same principles.
Don’t forget to thoroughly air-dry your rag if you are using one. We don’t want any fires.
Paint lots and paint well!