While it's still empty.......Rent a rotary floor scrubber and various abrasive pads and brushes to clean the floor.......
Invest in a good wringer mop bucket and a BIG cotton mop...........add some standard floor cleaner and scrub away..........Mop the floor until clean..........The suface will be "open" and will need to be sealed/refinished...........
The scrubber has a unique mode-of-operation......You'll quickly learn to slightly raise and lower the handle to move the unit Left and Right.......Often refered to as "dancing with a Fat Lady"..........You go where she wants to go!