I mix a lot of my own colours using baseline store bought oil paints (usually Windsor-Newton) (but not from the bottom-up with pigments - that's a fantasy I'll reserve for my retirement). Where I am experimenting with different qualities and lustres is in the media I use to dilute them - especially like walnut oil lately. But in the Resurrection Series I prefer to use as little medium as possible, to get more of a feel of immediacy. However, your eye is keen in that you've noticed there's something different about the Madonna painting, where I used quite a bit of medium in the paint, as it helped me cope with a lot of the underpinning painting - which was a rather strong image to overcome
What a great combo of outstanding talent: The photography of Gregg and the amazing oil painting by Olga! This is as good as it gets and, as always, I applaud you. Thanks for sharing and for the inspiration.