I think I found a new way to do studies more efficiently. Where I before put the reference image next to mine so that I could see it while doing the study, I tried this time to hide it and only take a look at it to know what to draw next. In effect I zoomed close to my picture and when I didn't know what or how to paint something, I panned the camera to the reference, took a look, tried to remember the thing and went back to my painting. That way I was forced to mentally say stuff like: "the wrinkles on the frogs shoulders are bigger than on his stomach".
Also it helped me to make it my version. I looked at a special spot, had an idea how to paint that and tried it. After a while I went back and compared. The whole time in between I didn't have the reference image telling me that I am doing good or bad. I just did what I thought was working and compared the result.
Maybe it is something worth trying for you too?
If you do I would love to hear if it did something new for you.
roughly 2 h for the toad.