Thanks Bill, It was a little challenging trying to make it all work!
I setup the camera, pushed the self timer, ran to pick the umbrella, spin it (sometimes to fast/sometimes to slow), and hold it steady. I tried to get enough blur to spread the black, but not give the recognizable "triangle" shape...Here's where it ended up Shutter speed: 0.3 sec / Aperture: 8 / Focal length: 24mm / AF mode: Manual Focus