My husband has bad shoulders and it is hard for him to do a lot of scrubbing. You can purchase it at the hardware store or a home center. Wash the floor down using a chamois mop and rinse.
Power washers are also great for painted garage floors.
Look for one when they are on sale. Janitorial supply companies and home centers sell sweeping compound. This allows you to sweep the floor, removing dust, oily dirt, etc. with out having it fly around. There are several varieties to choose from and it is wonderful for garage and basement floors. You can make quick work of cleaning the floor by sprinkling on the sweeping compound and then sweeping with a push broom.