Best pest control foggers according to redditors

Yes, you're right its a fogger. Probably for mosquitos.

https://www.amazon.com/SILVER-BULLET-NON-THERMAL-FOGGER-MOSQUITO/dp/B00VMGSHIS/ref=sr_1_4?keywords=SILVER+BULLET+ULV+NON-THERMAL+COLD+FOGGER+TRIPLE+JET+PEST+MOLD+MOSQUITO+FOGGER&qid=1564946723&s=gateway&sr=8-4

https://www.amazon.com/Longray-LR-2680A-Carryall-ULV-Fogger/dp/B003YKJGZI

This is the one I'm looking at. There are cheaper ones and more expensive ones. The reason I like the concept is that they are designed for chemical applications so they are designed to resist corrosion and what not. Not sure if they resist clogging if they are run for many hours non-stop or if they will still have closing issues, but I don't think they would clog as bad as some of the pond foggers I've been looking at.

> If I had botrytis (in its very early stage, so I guess spore spread wasnt "as terrible" as if it would have been on in a bad case) in my last grow, do you think I should get a new filter and exhaust fan?

IME, no need to go nuclear. But clean all gear, walls, floor, ceiling etc. And apply a botrytis-specific fungicide, heavily (as in drench). And, if the plants aren't in yet (or you can move them out for 24 hours), use a sanitizing solution. Mild bleach solution if you can (24 hours after dry, to let the chlorine dissipate. . .NO plants near in that window). If not, there are lots of sanitizers that won't hurt plants. Grow/Garden shops should have some.

If this is to be a long-term project/grow, then look into foggers. These can get insecticide/pesticide/fungicides into every corner of your grow. They do come with a hefty price-tag.

FWIW - I think the old fashioned foggers that work through a chemical reaction when you put them in water work a LOT better than the more common aerosols.
https://www.amazon.com/Johnson-Inc-1376912-Fogger-Fumgtr-35oz/dp/B000A0VUTK/ref=sr_1_1?ie=UTF8&qid=1499792695&sr=8-1&keywords=raid+fumigator+fumigating+fogger

As the others have pointed out, you need to get the water or excessive humidity under control, or this is going to waste your time and your money.

If you are in the UK, see if you can rent one of these at a local home improvement centre:

https://www.amazon.co.uk/Concrobium-Gal-Control-Fogger-TRI-JET/dp/B0026SZCCK

This will kill the existing mold and mildew, and the spores as well. Once it is all dead, you can wipe down all surfaces that had visible growth. But it'll be up to you to keep it from coming back.

What problems are you having? Spider mites and russet mites are the problems I usually deal with. Prevention is the key, the earlier you prevent and treat them in the early stages, the better! You should first make sure your grow space is as clean and organized as possible! Make sure your plants are not too bushy either, so propper pruning and some defoliation here and there will be useful. Plus it just allows better airflow for the plants, mites seem to love hiding and living in those spots crowded bush spots.

I aim to at least treat my plants once a week, often times twice a week especially in the summer. I use something like this:
https://www.amazon.com/dp/B07SBC1DQL/ref=cm_sw_r_cp_apa_i_9IWzDb4MW3KME

Or
https://www.amazon.com/dp/B01N64CO0P/ref=cm_sw_r_cp_apa_i_oLWzDbT5DY5HS

Fill that bad boy in with whatever chemical or natural pest treatment you like. I use the natural neem oil or azamax that everyone seems to like using. You can switch it up with other treatments too, just look up what mite problems your having and try out products that are used to treat it. Make sure to not just hit the top but also the bottom of the plants and canopy. This normally does the trick for me. It's fun using the machine too lol.