I suggest defog spay and a toothbrush. I put both in my mask box and use them before every dive. I'll emphasize the toothbrush because I have found that a No Fingers Policy with the mask is the biggest anti-fog improvement you can make. I have have numerous dives impaired by mask fogging, and eventually figured out that body oil and sunscreen from my hands was a major factor. So at the start of the dive day I give the mask a good scrub on the glass, skirt, and outside too with the toothbrush. It works great and I never ever get fogging anymore.