I've always used permatex or fast orange hand cleaner, whatever I have at the time. Scrub the stain with it let it sit for awhile then rinse. What it doesnt clean up you could cover with some baking soda to try and suck it out of the concrete. With normal weathering you wont be able to see it in short time.
Jason..Seriously Ugly UDS (it gets uglier every time it rains), Heavily Modded ECB, Weber OTG