PPG is selling its residential and commercial paint business in the U.S. and Canada to private-equity firm American Industrial Partners for $550 million. The Pittsburgh-based paint and coatings company also said it would lower costs by closing facilities and cutting 1,800 jobs, mostly in the U.S. and Europe. In February, the company announced a strategic review of the house-paint operations, which include brands such as Glidden, Olympic and Liquid Nails.