Good questions.
All you really need is one spray onto a jig.
And all I can say is, it stays on a long time. But having said that, I usually reapply every dozen or so casts. That way I know it's still on. You could prolly wait for two dozen casts easy. Check out this video. It's not a good video, but it's there. It was my first attempt at capturing the Slabsauce staying power. Can't video and cast at same time so I had to ask wifey for help, which just makes it all more complicated. Anyway, here's the video: