Using Mark's recipe for slow dry medium has really helped me as a painter, however I am looking to begin painting with paints that have a greater variety of body/thickness. I would like to be able to keep the slow drying time provided by SDM but also be able to apply thin liquid layers as well as thick impasto ones. (One concern I have about doing so is that thin liquid layers, even if mixed with additional solvent, will not dry quick enough to follow the fat-over-lean principle due to the properties of SDM.) Here are my questions:
1) Thinning: My instinct would be to thin out paint already mixed with SDM using additional mineral spirits or potentially a 1-to-1 mixture of mineral spirits and refined linseed oil. Is this an acceptable technique to use? Will the addition of mineral spirits increase the drying times of thin under-layers enough to adhere to the fat over lean principle.
2) Thickening: Does anyone have any recommendations for how to thicken paint that's already been mixed with SDM? Would an impasto medium work? I'd like to be able keep a similar slow drying time but I'd like the paint to be much thicker so that I could lay down more impasto brushwork that would keep it's shape and not level off.
Thanks so much for the support of this community, and for your help!