get the Army in to do it. For free. Only cost to you is the materials.
From 538 Significant Digits:
30 days
Members of the military deployed near the U.S.-Mexico border have been assigned to paint a mile stretch of border barriers in Calexico, California, in order to improve their “aesthetic appearance.” The painting will last about 30 days, and the paint and equipment are estimated to cost $150,000. In the past, some barriers have been painted white, which officials say makes it easier to spot migrants, while President Trump has urged for them to be painted black so that they absorb heat and become too hot for migrants to climb. [CBS News]