Not exactly a tutorial so I posted it here. I long ago discovered the value of working in greyscale and adding colour on overlay layers. This enables me to concentrate on getting the correct tonal values first. The image can then be flattened and treated like a normal painting. I also open a new view, reduce it to a thumbnail and pin it with Deskpins enabling me to see at a glance whether the composition and values are correct, even when zoomed in on the main window.

Pretty smart using Deskpins like that

I think GIMP's ability to show multiple views of the same image is one of its neatest, and most underused, features. Another feature that often goes unnoticed is tearoff menus -- which can make customizing your "thumbnail" view much simpler (why have menus, rulers, scrollbars, and status line in preview?).

Here is a short video showing how this can work.

http://www.kerosenecow.net/videos/multiview/

I knew about tear off menus but I didn't even think to remove the scroll bars etc. Thanks for that.

I wish I could get rid of the title bar. The video doesn't seem to show one, even on the main window.

That is a feature of the window manager I use.

I see you're a Linux user. When I finally make the switch I'll go for that, in the meantime, I'll just have to put up with the title bar!

I have a question.
In Gimp-2.7.6 how do you open a new view not tabbed in single window?
When it's in single window mode it seems to be impossible as it always opens as a new TABBED image.
If you take it out of single window mode it works okay.

I see what you mean. For some reason, I once thought that you couldn't adjust the toolbox width in single window mode and now I know you can, I would like to use it but I can't work without a thumbnail view of my painting. I hope there's a way to open a new view separately.