Sketching Quickly - Barges on the Rhone

Over the years I have developed a technique for sketching quickly. There are a number of reasons for this;

I often sketch from a moving boat or vehicle and you have to be very quick or the subject is gone.

The light can change quicly and the shadows will move around, although you may wish to change them anyway.

Alex is patient but not for long and a "Can I just do a quick sketch?" is always met with "Yes of course." But it has to be quick, minutes or I am pushing my luck.

Anyway the way I do it is to mentally access what I want in the picture and lay down a few guidelines in 2b pencil. Then I get my travelling Cotman watercolour box and an aquabrush. I block in a few colours not being too careful about going over guidelines. I then block in the shadows. Lastly I delineate and emphasise some shapes with a drawing pen. Whole process 5-10 minutes maximum. The crucial step is getting the picture in your head before starting. I had moved the barges shown nearer the bridge than their actual position for my composition. Of course there are numerous ways to do sketch and this is just my own quick method.
The sketch is on the Rhone at Avignon.