Use a mop and a pH-neutral cleanser to remove any dirt or debris from the brick floor. Wait about four hours for the bricks to dry.
Mask off any surfaces adjacent to the brick floor to avoid over-splash from the painting process.
Open a can of acrylic primer and stir it thoroughly with a wooden stir stick until there are no signs of streaking or clumping in the can. Pour the primer into a rolling pan. Dip the paint roller into the pan to saturate the roller head with paint. Run the roller over the pan to remove some of the paint.
Run the roller over the surface of the brick floor, covering the brick completely with the primer. Choose a primer color you don't mind seeing, as the distressing process will make it visible through the painted topcoat. Switch to a paintbrush when coverage with the roller isn't possible, such as covering mortar lines or the edges of the floor surface. Allow the primer to dry overnight.
Use the same application process you used for the primer layer to apply a topcoat of paint. Allow the paint layer to dry overnight as well.
Randomly scratch up the surface of the paint on the bricks, using a handful of steel wool and sandpaper attached to a sanding block to begin distressing the floor. The more areas where you apply the abrasives, the older and more worn the brick floor will appear.