Impasto medium by Winsor & Newton is a delight to use with their wm oils with SDM.
Makes a nice gloopy paste without changing color. A thick lump can be formed into soft peaks.
I had about 5ml left over green on my palette to which I added about 5ml of impasto medium. Mixes easily and quickly. The surface loses the oily sheen to become a matt lustre, but the shiny lustre returned on drying.
I mixed this sample 24 hrs ago and it's not quite touch dry. I suspect that the Oleopasto variety and tube artists color would dry glossy in this time frame.
I used some ZestIt solvent to adjust flow consistency off the brush. It works as advertised as a solvent without odor. Better still it dries, more slowly than the turps varieties I've used and evaporates to leave a durable paint surface. Quite effective as a brush cleaner too. Have not tried ZestIt with clove, linseed, stand and VT yet.
Finally i have have been lucky to discover an excellent brush cleaner and brush conditioner.
These products are probably not available where you live, but look out for the key ingredient of hydrogen peroxide (HP). Many products use HP along with water and a detergent.
Both of these products removes any paint residue, oily remnants or gummy buildup on the brush fibers.
Worked through about fifty of my brushes with a small amount of product with a warm water rinse and towel dry. All are now soft pliable and so clean.