2016 Golf preventive maintenance for sun roof leak

Our 2016 Golf recently had a leak around the sun roof which caused some staining of the fabric on the ceiling. Fortunately, it was fixed under warranty. The service manager told us that the water drains for the sun roof are small and need to be cleaned out periodically. He suggested that we pay them to clean the drains every year or two. My question is this: Exactly where are the sun roof drains, and is there a simple way for me to clean them?