TonyM according to the internet content of that medium it is thinner and linseed oil.
Adding it with a bit of more thinner is one of the ways to go. No chemical conflicts in it.
You can vary proportion of linseed to thinner to reach objectives you set for yourself.
linseed will make it more slippery and will bring more gloss when paint dries.
thinner will allow to work in the first layers and will have matte finish. If you dilute with thinner use it for sky and mountain and dark base everywhere else. Try to make layer of paint thin, let it dry for 30-45 min to allow thinner evaporate. Then go with oil paint mixed with medium/thinner for your highlights.
this is just one another option.
if what you do works and you like it -this is the way to go.