Look up 'guano tea' if you are already into flowering.
When I use guano, it is always as a soil amendment- a couple spoonfuls mixed into 3 gallons of my compost mix is the final re-pot, done anywhere from the start of flower, to about 3 weeks in, depending on how big the plant was when I started.
But yeah, it is the shit for flowering. My friend always laughs at me when he sees a jar labelled 'bat shit' sitting up on a shelf over my kitchen sink... what can I say, that stuff is pretty darn useful!