A technique I use when painting from a photo is to look at the painting and the photo up side down. I find it helps to show what is out of place and lets things stand out that you may not have noticed otherwise. Or squint for a long time. Another favorite is to get out my mobile phone that has a camera on it and i look at the painting through the phone which again reveals things i wouldn't have noticed about the picture.my
Here is a piece i started today.