Painting an old concrete floor is a fast and cheap way to make your basement look a lot cleaner and overall nicer. Most of the time is spent with prep work.
Sweep and mop the floor very well before starting
I used Valspar Fast Prep as a floor cleaner, it worked well
I also used some water and a bucket, a scrub brush, and some gloves
Add some water to the floor, pour on some Cleaner, then scrub the floor
After cleaning the floor get some fresh water and mop it again to revome Fast Prep residue
Get a roller of at least 13mm or 1/2 inch nap for rougher surfaces
Don't use a fancy brush, just get a cheap one
Use the brush to cut around the walls
After cutting around the walls, use the roller to paint the floor
Let the first coat fully dry
Cut in the second coat of paint
Roller on a second coat of paint
Let the second coat dry
Two coats should give a good finish. If not consider a third coat