I used to use a fogger with canola oil and 5% thymol dissolved into the oil. I felt it worked real well, even counting mites on sticky boards comparing fogged hives to unfogged hives.
It worked when I only had thirty hives and I could fog them every seven to ten days. The more hives I added, the harder it was to get to all my hives to repeat the treatments. I feel it takes frequent fogging every seven to ten days, and I fogged my hives five or six times after the honey came off. I fogged during late July through early September.
But then as I added more hives, I had more production. I was spending more time at the farmer's markets. Hives were not getting fogged on schedule, so I switched to formic acid in Mite-Away II pads.
This topic is rather controversial. It used to be more popular, or at least "discussed" more often a couple of years ago (check the archives). Seems like it also dropped off the radar at most of the bee meetings I attend.
Thyme Oil is not what you need for fogging. You need to buy "natural" Thymol crystals, the Thyme plant extract, not "synthetic". You don't want to harm your bees with the wrong product.
Take some time to read up on the studies done with Thymol fogging. There are specific measuring and mixing instructions you need to follow, using the correct product. Google " Thymol Fogging Rodriguez " and you will find plenty of good reading that will answer most of your questions.
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