There was one artist Nathan Fowkes brought up several times over 4 days: Richard Schmid. If you're not familiar, he is a giant of American realism. If a master painter and composer like Nathan Fowkes recommends an artist I'm definitely going to listen!
Nathan likes to use black prisma on paper to do his tonal studies so I tried to model his process here. No audio here, I will make a proper version with commentary for my YT soon.