All the colors I use are opaque and individually mixed. Their transparency is an illusion created by extremely careful color mixing.
Working on the colors is a balancing act between my knowledge of the colors and how they work in mixes, and the tiredness level of my eyes.
Does it take unbelievable amounts of patience to do this? Yes and no. I find it meditative and calming more than frustrating.
This composite of my painting table is a portrait of the mixing process: chaos and calm.