You don't have to make a tea with it. The guano is aged and already has significant amounts of plant available P in it. My Indonesian guano is a 0.5-13-0.2, so 13% available phosphate according to the packaging. P and K are typically always listed on fertilizers as 'Available phosphate' and 'Soluble potash', with both percentages listed being for the oxide equivalents, phosphorous pentoxide (P[SUB]2[/SUB]O[SUB]5[/SUB]) and potassium oxide (K[SUB]2[/SUB]O)... while N is described as elemental nitrogen and typically sub-listed as the soluble vs. insoluble portions.
How much you should use depends on how large your plants are, how they handle nutrients and how far along into flowering they are. Also, how much P is already in your soil and if you're using mycorrhizae. Myco gets lazy when there is too much P in the soil, because they like to go seek it out for the plant. If you have a larger plant (over 4 ft) that is kind of a nutrient hog then you can use the 2-3 tbsp per gallon. If your plant is smaller and doesn't appear to need that much, and\or you have mycorrhizae then you should probably just use a tablespoon to a tbsp and a half. If you're not quite midway through flowering you can use a bit more and wait a few weeks instead of a couple to reapply if it doesn't look like your plants need it. If you use humic\fulvic acids, you should use less guano because these are organic chelating agents which will help the plant roots assimilate nutrients.
Remember the plants need more than just P for optimum growth, they can have all the P they need and the buds wont grow to the fullest extent unless there is enough of every other nutrient they need. Sufficient potash is also quite important, and of course trace minerals as well, so provide some kelp and molasses along with the guano. If they're in early bloom also be sure to provide some nitrogen if there isn't enough in the soil.
