Having made some decisions about my approach, I've started sketching in the shapes. This is going to take a while.
The biggest decision was whether to tone the canvas first. I feel like whenever I work on other than a pure-white ground, the resulting painting looks murky and dirty. On the other hand, this is a murky and dirty building! I want the sense of layers and undertones, fish grime and dirt. Mmmm, fish grime...
The sketch is done with a #6 round paintbrush. I used Cerulean Blue. I don't use a pencil for sketching anymore; going right to a brush starts it off in a more painterly style. Pencil is just too tight.
My plan is to do a fairly detailed, accurate drawing, and then paint in a looser manner. We'll see how that goes.
I've posted progress photos before, but only after I'd finished the painting and decided it was showable. This time I don't know what we'll end up with!