Depends per person, but usually 2-4 sprays per product work fine. To know where to spray, usually Application points 101: a guide to where on the body to apply pheromones will help. Some sprays (especially the 20% perfume ones) can come as very strong. I would suggest to wait 30 minutes before going out, to diffuse the smell a bit. What I do is start with a good shower in the morning, dry myself, spray the mones, get dressed, have breakfast and then go out. Clean guy with a fresh smell, ready for work 
I usually spray Ammo on my chest (less diffusal) and I suggest to put IS on your neck for self-effects Sprays usually last 4-6 hours depending on where you spray them, but had self-effects of some sprays after 8 hours. As long as you smell the spray, someone else will smell it too