Say you have made fastpasses. And now it is time to use them. How does that work? Scan magic band, then is there a separate line or you wait in a fast pass line? Can you explain how it works for the ride in the park?
There is a separate line for FPP at the attraction entrance. The other is standby. They are well marked. You scan your magic band (Mickey head to Mickey head), if it turns green, you enter. Blue means no (no FPP, wrong time, etc). Then you walk through that shorter queue to the ride for loading. CMs will load from both lines, maybe giving preference to FPP folk. As soon as you have scanned to enter, you may make another FPP (after you have used your 3 advance FPP). You do not have to wait until you exit from the attraction.
Is there ever a line that you have to wait in the FP line?
Sometimes it gets backed up because people do not have fast passes but the line usually moves. There will be short lines and then before the attraction you usually merge with stand by.