I use this every day, but I also shower at night and ""no-poo"" my baby fine hair every few days. If you do not, then the fibers might get on your pillowcase.
With a new bottle, I peel off the plastic tape that is covering the shaker, then tape off 1/2 of the opening with blue painter's tape - otherwise too much will come out too fast.
You do not actually shake this on to your hair, but instead into your part lines. Part your hair, hold the bottle at 45 degrees or so, and gently tap the fibers into the part while holding your other hand over your forehead to keep fibers off from there. You may have to do a quick wipe of your forehead with a tissue. If you have a lot of fibers on your forehead, you are tapping too much and too hard - or you didn't seal off 50% of the shaker with painter's tape. It does not take a lot to make your hair look fuller, just a tap-tap-tap and them move on to the next area.
This would not work well for extensive baldness (nothing does!), but works well for the dreaded ""wide part"" problem. Dark hair would be more of a challenge on a light-skinned person, as the contrast between hair and scalp would make the fibers show more than with medium brown hair.
They have a really small travel-size that I carry in my handbag, so you can try it without spending much $...you would not have to tape the shaker part on that one!