I was reading a few tutorials and they mentioned Over Painting (Or Paint Over), something like painting on top of the reference picture (like tracing but with colors instead of lines).
As described in this video tutorial (start at 9:44 https://www.youtube.com/watch?v=hHfJCvAPqlw ), he basically uses Matte Painting and then paints on top of it.
There are also these anime background tutorials, using a similar technique: http://www.mclelun.com/2015/11/anime-background-paint-over-photo.html And here: http://www.mclelun.com/2015/10/anime-background-tutorial.html
The problem is that neither author specifies how to do that.
I tried to create a new layer on top, use the color picker tool to pick the colors from the lower (reference) layer and apply the colors with various brushes with different settings (opacity, flow, wetness), but it's always confusing, since the top layer end up covering the lower layer (reference), and I can't tell which is which.
I tried to reduce the opacity, but it makes it even more confusing and also messes the colors since they become different with lower opacity.
Does anyone know how to do that in an easier way?
Thank you very much :)