I did the full fitting in one session mainly because I was concerned I was in the wrong shaft for both irons and driver. I had my son fitted two weeks ago for irons only and there really wasn't much difference in the amount of balls we hit. However, he tried 3-4 different iron heads and then went through 2-3 shaft combinations, where I was zeroed in on the AP2's and dialed in the shaft. I was going to swing the CB, but after feeling the AP2's, I had no reason to try anything else. I was coming from 962's for 14 years and Hogan blades for the 15 years before that, so I wasn't going to experiment much.
So basically, he tried AP1's, AP2's, Taylor Made, Ping, and then worked through 2-3 shaft combinations. While he absolutely kills the ball, him trying several iron heads was important to see what he liked and felt best swinging.
I hit AP2's and moved through three shaft combinations until we got it right. Moved on to wedges to get the right bounce setup, and then moved on to Hybrid and Driver. By the time I was swinging the driver, I was a bit fatigue'd, but hit enough good ones to dial in the right combination.
Also, all irons are done testing the 7 iron. They get launch angle, spin, ball speed and pretty much dial it in from there. You don't hit every iron in the bag. Gaps are easy for them to figure based on your 7 iron distance. My old set was 3-P, with a 56 and 60. My new set will be 4-P, +Gap, 56, 60. And that is perfect as I had a big hole in that 100-125 range.