Thank you, that was really helpful!, however I still think it could all be done in Painter (?) I use Painter, and the reason why I'm interested to understand the advantages of Photoshop is because maybe I could also use both to improve my pieces, that's why I'm asking. Thanks!
Not really - I tend to block in the colors on the layer below the line sketch and then paint on a layer above the line sketch until I'm reasonably happy with how the piece is going, and then I still tend to do adjustments that I may or may not want to keep on layers as well. I just tend to merge them all down periodically when it gets unmanageable.