Once I have a photo of the painting at whatever stage it's at, I can add and
remove elements easily in PS using layers. That way, I try them out but they're not a permanent part of them and they can easily be left omitted.
After I did this much, I used PS to see how the dragon fairy at left of center dragon would look in a blue green blouse instead of the red color I gave her with colored pencil in my prelim sketch. Unfortunately, I didn't want to keep it, didn't save it and don't have it to show you. But now you get the idea. The picture has progressed further since I took these 2 pics. More may follow as soon as I get pictures to show you.