Commercial flat roofs need specialists to avoid future issues. Check out this directory:
Roofing Contractors in San Luis Obispo, CA. It includes companies experienced with flat roofs, single-ply, torch/PVC systems, and commercial jobs. I manage properties and used one for a similar recoat — they did inspection, fixed drains, applied quality coating, and gave 10-year warranty. Very professional, on time. Get references and verify insurance for bigger jobs.