You do need to shake the can for the full two minutes as the instructions say. And, I have found, it needs to be used at the correct temperature, otherwise it comes out in clumps or it doesn't stick well.
It sounds like maybe your spray nozzle is clogged? You can pull that little plastic nozzle straight up and off and soak it in alcohol or something like that to open it up again.
I find that I need to use something oily or abrasive to get the spray off my hands. Like a baking soda paste or even vegetable oil. Or a combination of both. I try not to use solvents on my skin as they can really irritate the skin. lol
Rest assured, it won't gun up the needle. However, I think it takes a few washings for it to come out of the quilt entirely. But, it is on the inside, so you will never know. It doesn't leave an odor or anything.
Good luck. :)