I use the term 'brush' because that is the name of one of the most common tools used in graphics tools such as photoshop. A brush is used with similar tools such as a pen or fill tools to color in areas on graphics or do something like dodge/burn areas of photographs. They're used for all kinds of things allowing you to 'paint' the effect you want allowing all kinds of control like brush shape, flow, opacity just for starters. I use them a ton with layer masks in photography.
Below is a simple example of a dark grey brush with opacity set around 85% that produces softer edges and allows the value below (in this case white to be seen underneath). I also passed back over it with a few strokes to darken in areas to the left.
Anyway, tools like this are used extensively when editing images with a mouse or a pen tablet. Typically you're not painting color directly onto an image, but often you're lowering or raising values that already exist in the image. I can see 'strokes' like this in many frames on the Altima video that look artificial to me. I think they've burned down some of the window views to cut out a clearer view of the occupants. Still JMO of course...