Guys if you don't have a Sweeping Company to clean before you or can't get one, Use a BACKPACK BLOWER to move all the dirt to one end and clean it up with a Broom, Trust me it will save you tons of time moving Mud Around. I Blow most of the places before washing and it makes the job look better to without as much mud run off.
Ron where are you finding a Broom Sweeper that fits into the parking garage? Is someone down there running one of these, my new one fits into them but it is vacuum and does a nice job if they know how to run it right.