I went to the Magic Kingdom on July 3'rd and was the runner for my group. At park opening, I went straight to Space Mountain, while my group went to Dumbo to start the day off. After getting the Space Mountain fastpasses, the next return time was 10:05 AM. I met my group and we did the fantasyland rides (virtually all of them), and then I showed them where the Princess line was and began the walk to Splash Mountain around 9:55, timing it so that I'd arrive at the FP machines just as I was eligible for new fastpasses.
Once you get the first two out of the way, keep your eyes on the time on the ticket where it says you can get a new fastpass, and keep accumulating them.
The late morning and afternoon is when the runner will be doing the most work getting the fastpasses, but theres' a big reward involved with this, and the evening was a godsend.
We got a spot for the fireworks, and then when that was over, we did Buzz fastpass, Space Mountain fastpass, Space Mountain fastpass, Splash Mountain fastpass, BTMR fastpass, BTMR fastpass. All of the lines had post times of at least 30-45 minutes, if not more, and we virtually walked onto every ride.
The park was open late on the 3'rd to non-resort guests (1 AM), and it was an EMH night there when I went, but by attacking the fastpass machines as soon as you're eligible to get them, while saving them and using standby to ride Splash and Thunder in late morning, you get to ride the top rides 3 or more times in the same visit if you have two or more fastpass return tickets for each member of your party.
I was thinking that on July 3'rd, the fastpass machines would run out quickly, but the plan worked to perfection.