You have to whack it (closed) a few times before using it each time after it's initially loaded. If it's a new pad, you have to "charge" it (whack!) a bunch to get the powder flowing. The basic method is: whack whack, swipe/rub on stencil for a bit, then close and whack whack, swipe, etc.
Usually you only mark one area at a time, quilt, then mark another area. You can't mark a ton at a time because it can bounce off pretty quick during the quilting, especially if your fmq foot is a hopping foot. I really don't like gliding feet but that would preserve the powder better if you do like/have a gliding one.
One thing I had read somewhere was after marking, to lightly spray with hairspray to keep the powder on longer. I haven't had issues with the blue powder washing out except one time when it was a gift for a student's mother going through chemo. That was no fun. I always wash in warm water with soap and that time, the blue didn't all wash out! On successive washes, I also tried using Dawn, lightly scrubbing with a toothbrush, and eventually gave up after the 4th or 5th wash. It was mostly gone but still noticeable in the stitch holes but I couldn't spend more time on it.