This was an idea I got from Matthew White on YT. I bought a little bleed proof marker pad and 4 warm grey markers and make these value studies on the spot as i wander around. They take ten minutes each max, no pre sketching, just dive straight in - its fun and quite addictive and very handy. I made these below in one stroll home from town to home.

What they do is abstract reality enough so as to provide the basis for a painting, so you can work from these with the photo as support rather than be a slave to a reference photo and get bogged down in details. I purposely try to represent three values to represent lights, midtones and darks. You will need to squint a lot, ignore the edges of actual physical things and focus on the values, if a building and a tree are the same value, draw them as one connected shape. Thats your 'lost edge'.

It also trains your eye to spot different compositions you may not have noticed before. I'm yet to take one of these to a painting, as I just began with it, but some I will for sure. I think its especially beneficial in an urban environment, to help remove unwanted clutter from a scene.