How do I get rid of concrete/drywall dust?

Look for a deck drain (floor drain). Basements usually have a drain. If you find one use a hose and wash it down. If there is no drainage and your water proofing it then you should be putting in a drainage system. In brief- rent a concrete saw, wet cut a corner about 4 x 4 feet, dig out, the deeper the better, add drainage hoses and drainage box, all can be bought at a Home Depot type place, replace soil with pea gravel, call a "spill over truck" (phone book under concrete companies- tell them you need 1/2 a yard), pour and finish. 8 hours if you call days ahead on the concrete truck. You'll be hauling off old concrete waste too.