I refresh consistently for a few minutes and pretty much can get whatever I'm looking for.
The best way to search for a specific ride is to book the first time that pops up for the attraction you want. When you then go to modify the time, that attraction will appear at the top of the list. This obviously only works if a time appears, but most every ride has at least one time show up after a few refreshes.
So last night I was trying to get a Space pass to start around 7:45 to match with some friends who had booked before me. I scrolled down to Space, it was unavailable. Refreshed, scrolled down, saw for 10:30 and booked that. Then went to modify the time, and now Space is at the top of the list - no scrolling necessary. I tend to book increasingly earlier times (1030->9, 9->8:45, etc) because it makes me feel like Im making progress, but it's not really necessary