Okie, we are again getting a little off topic or at least into the sticker bushes again with this discussion.
It is inevitable that somewhere in the course of trying to communicate with each other that we will committ certain faux pas. I think this one has played itself out on our stage and we should move on with talking about underpainting.
Marvin: The Covino method which I learned had me using liquin or Galkyd in the underpainting and a medium based largely on Damar and Venice Turpentine for color. I used it, but did not like it much as it really dragged on the brush after about 30 minutes.
I have since changed to using Marogers medium (black oil and double mastic) for my primary medium. I swapped out my turpentine for oil of spike lavender. I understand the risks that Marogers can pose if it is not formulated correctly - I believe my stuff is formulated very well. I love how it handles. It stays open and wonderfully workable for most of a day and is touch dry the next day. Strokes are really smooth and it dries with a slight gloss which I find appealing.