Last year I hired a concrete crew (friend of a friend) to extend my front porch. In the process, they splattered concrete all over my front porch -columns, windows, front door & the brick. I've been able to scrape the splatter off everything but the brick. I had NO luck getting the crew back out to clean up then or now. Any suggestions on how to clean up the brick...without messing up the morter holding the bricks together???