Messiest thing Arthur has ever done. and he loved it! I just used paper; will do someday with canvas---Snowflake canvas art. Do a whole series of kid Christmas canvas art projects! Blue = snowflakes. Green = tree shape. Yellow = star. Red = wrapped present shape or ornament or holly. Kid art - just remove the masking tape when the paint dries (or before, works both ways).
Also on these boards
Removing Oil, Paint and Other Concrete Stains Remove oil and grease stains from concrete using TSP and other cleaners.