I have practical experience with B+W (including Kasemann POLs, F-Pro, slims), Hoya (HMC, SHMC, HD), Tiffen HD, Canon, Nikon and Zeta (as good as B+W without the price tag). They all will fog. So do lenses and viewfinders. The difficulties you speak of are very common, not unusual and something photographers have to deal with in the field. I have experienced that immediate fogging in rainforests with all filters due to cold conditions in New Zealand and closer to home. Take the filter off and shoot without it. It is most unlikely there will be any adverse effect from leaving the filter off for a shoot; put it back when you have finished. That's what I did with any and all of my L-series lenses if they fog.
The coating on the lenses is an entirely different and specialised beast and on Canon lenses (all of them), fogging can and does occur in cold and humid conditions. There are anti-fog solutions on the market designed for glasses wearers; you might want to try this on the front surface only of filters and see how that goes.