I have slowly found that a few drops of linseed oil is just enough even to be distributed within the other paints for a while, or, it would be enough for a single session of paint, depending on the size of the surface.
something I have encountered trouble with is a certain clumpiness of the paint. I have figured this occurs without thinning, or the fact that it is on wood panel, but if anyone has advice on how to remove these small crumbs successfully, please let me know.