What the Asia divers do on my island. Take Joy dishwashing liquid coat inside of mask with generous amount. Let stand face down in the sun for 5 to 7 days then rinse. The Asain divers say only use Joy diswashing liquid that is the only brand that works. The 70 some Asain Dive shops on Saipan do this to all their new masks before being sold. I have tried this with my own masks and it seems to work quite well.
Dale Still on a little rock in the Pacific next to a pineapple under the sea