Most horse's hair only grows about an 1/2 inch a month, so 6 weeks isn't really long enough to see a visual difference, short of measuring it. Granted, some horses grow more or less than that in a month. I've never tried the M-T-G on the manes and tails of my horses because they do not need it, the only thing that I have used it for is rain rot, and it worked beautifully. What I do, if I want to get my horses manes or tail longer, put baby oil in them, and get it completely combed through, and make small loose braids in the mane, and just braid the tail. I have found that that works for me.
I use the small braids because I've had better luck with them than the large ones. But, to each their own.