The whole sketch took me about 4 hours from start to finish. I found it a real challenge to depict the subtle light variations that Caravaggio's art is known for. I think this is because I'm still such a novice with Painter. Overall, I avoided using the opacity sliders and just tried to lay down thin glazes of oil colour (I did this through adjusting the pressure of my stroke with the Wacom pen) and mix them naturally using the Mixer palette. The whole piece is done on one layer. For now, I prefer keeping things on one layer because it duplicates the feel of a traditional painting on canvas. You could say that at this early stage I'm trying to forget I'm on a tablet and just paint as if I would on a canvas. Oh, and the brush work is not nearly as blendy as Caravaggio's original with all those thin glazes of oil. I was just discovering the Real Bristle Brushes and restricted my use to the Real Flat, Real Oils Short, and especially the Real Flat Opaque brush. I also used a Fan brush for some blending, and the Real Blenders. Overall, I learned a lot with this painting (I learned what the Mixer palette was, for instance, and about a few more brushes); however, in the future I am going to try to create smoother gradations. If that means resorting to opacity sliders, I'll give it a try.
If anybody out there has any great tips on how to Blend in Painter, let me know! I'd love to hear from you!