1/4 cup water per small packet. Nuke in the microwave for about 15 seconds.(depends on your power rating) but remember to not let it foam up.
On hickory remember to wet the bow before applying the sinew. Just wipe down with a wet rag before starting. Hickory will suck the moisture out of the glue too quick and can cause a failure down the road. Been there,done that.
One pack per 1/4 cup is a good batch to work at a time. Keep it warm but not hot.I use an old coffee maker to do that but be sure to place washers or something on the burner and set the glue pot on top of the washers. Otherwise it will get too hot and "curdle" your sinew.
Almost forgot- you want to rub some warm glue over the surface of the bow before laying the first course. Sort of like "booking" wallpaper.