Thanks for the acolades, Brian! When I figure out something that works I like to post it so others can copy it if they like. Not sure what part of the SF Bay Area you're in but here's a listing of TSC outlets within 100 miles. Nothing close to SF though. Graingers may have it. A word of caution though. Don't get the Black Diamond medium grit. It tends to clog at the nozzle. Get the fine or extra fine. All my local TSC had was extra fine which is about 80 grit. It flows well and works great!
Tractor Supply stores near SF Bay Area