Here's a quick lesson in using photo references, drawn on my Samsung Tab A with S Pen.
I'm using layers here, so the rough lines are drawn on one layer, then the clean 'ink' lines are drawn on another. I then use a separate layer under the ink lines to lay down the flat colours and so on. I'll make sure I produce a more in depth lesson in using layers some time soon!
Click on the individual images to see what's going on: