To get overspray off of concrete you can take that 4-5 ounces of left-over battery acid from filling a non-sealed battery, gently pour it into a gallon of so of water, and very carefully brush it on the overspray area with a shop broom.
***Make sure none of it gets on anything you don't want to etch with the acid, like your eyes, fresh paint job, wife's car, etc...***
Once it has stopped bubbling, soak it up with some absorb-all and dispose of properly.
-or-
For a more environmentally friendly way, get some snow from the driveway, and scrub it into the overspray with a shop broom. More effort, but works...eventually.
Thanks I never even though of chemical removal; I kept it wet when spraying, unfortunately some of the Por-15 is water activated so did not help
Say what is "snow"