Well, the first thing you do when you scan into the park is buy MP, then you get your first FP. It should have a pretty short return time - less than an hour, even for RSR. As soon as you scan in for your RSR FP, grab your Indy FP. I'd be surprised if your return time for it is later than 11:00 - I'd guess more like 10:00. Seriously - even though FPs ran out around 4:00 in the afternoon over Christmas, we still had a bunch all throughout the day and into evening. Don't forget the single rider line, too. It's pretty helpful!
IMPORTANT NOTE: If you're going onto Indy, GotG, Soarin' or any other lengthy ride in a cell-free bunker, DO NOT walk into the building after you've scanned in your FP UNTIL you've booked your next one. Otherwise, you'll sacrifice the 20+ minutes of ride experience time during which you won't be able to get another FP because of connectivity issues.