If you have park hopper, you can pre-book one or two FP ahead of time, once the first FP is used in the first park, you can use the app to book the third FP in another park though you are still in the first park. I am only interested in TSMM and ToT at DHS. I can book these two ahead of time. Once I scan my first FP, I can try to book Test Track for later.