Howl of Shabiri

So I heard this us a damage boosting incantation. Anyway I tried it out and there was no increase. I was then told that you have to get madnessed. So here's the thing, when I use it, the madness buildup is slow (it took around 4 or 5 uses to apply madness to me). Is this how people are using it? Or is there some way to make it instantly madness you?