I found a solution.
My garage is somewhat sloped to drain water onto the driveway. So, as long as I spray carefully and avoid getting the walls wet, washing inside of the garage is a non-issue.
During hot weather, the cement absorbs the water pretty quickly. Any water that remains after the wash gets squeegeed out. I also leave the garage door cracked for a few hours to vent out any remaining moisture.
Still looks good after over a year:
My garage is somewhat sloped to drain water onto the driveway. So, as long as I spray carefully and avoid getting the walls wet, washing inside of the garage is a non-issue.
During hot weather, the cement absorbs the water pretty quickly. Any water that remains after the wash gets squeegeed out. I also leave the garage door cracked for a few hours to vent out any remaining moisture.
Still looks good after over a year: