It would help me to better advise you if I knew exactly in what way you feel you have been unsuccessful.
Has the fog disappeared from your photograph? Or is the problem that your picture is foggy?
I have done lots of fog pictures in color, primarily because the client wanted pictures of the fog. Removing it with filtration seemed counterproductive to the assignment. And enhancing its density, unnecessary.
One problem with b&w is that it functions as a result of a key light (the sun) which provides texture, plus a fill light which opens the shadows. Remove the key light and you have no detail. And nothing from Tiffen will fix that.
This is why a field of snow on an overcast day has no hills and dales. Just pure paper white. And burning in gives you only pure gray mush. Same with a foggy scene: no detail, no texture.
My experience with fog is that it doesn't sit around in big white piles like 800 pounds of Cool Whip. In fact, it is not actually visible. The only visible effect is to remove detail in relation to its distance from the camera. A tree in front of a house becomes a tree in front of an off-white background.
The major advantage to fog is its ability to remove unwanted detail, like power lines travelling through the virgin forest. Or graffiti on an old train bridge. But aside from removing detail, it is not actually visible as an object in itself.
If you want dramatic, phoney fog, rent a Mole Richardson fog machine from a cine supplier in Hollywood. It will spray out liquid "fog juice" through a basket of dry ice which cools the white fog/smoke and makes it hang as small dense puffy clouds in the air. This effect, from the movies, is perhaps what you were expecting, not real fog in its natural state?