When he wants to paint an urban scene, he sets up his canvas right on the street and deals with the wind, changing light and other distractions. Here's his painting Gran Via, with the cars and people typically deleted.
Note how his painting surface is nearly 90 degrees away from the view of the scene. And note the unusual device he uses for measuring slopes and lengths. He rests one end against his cheek to get a constant unit of size.
One thing that might have helped him with the curious crowds would be to set up stanchions or traffic cones. I try to bring my cones when I'm doing street painting, and they look official enough to keep people back. Uniforms help, too. It also works, if you can get away with it, to set up on a flatbed truck or the back of a pickup to get a little protection from the chaos.
Previously on GJ: Traffic Cones