Look for a photo that has a section which would lend itself to a wet-on-wet treatment like what we were doing at the end of class. The attached image has the big rock, which could be done with three or four consecutive applications of similar, but successively darker color.
Put down a wash of the lightest color that covers the whole area. Make sure it's wet enough to stay wet for all the applications to come. Now add some more pigment (but no more water) to the brush, and lay in the next darkest strokes. Then more pigment, and the next darkest bits. Keep going like this until you have applied the darkest darks. This is not meant to be a proper painting. Just paint the section that suggests the monochrome wet-on-wet approach. Stay loose, and don't correct anything. If you don't like what happens, take notes (identify what went wrong, in terms of the relative wetness of brush and paper), and try it again.