I don't rush, but I also don't dilly-dally on the scale. Slow and steady win the race. I pull onto the scale with the combo hitched up like normal. I stand on the truck's running boards in order to reach the call button. That gets my first weighing.
For a fifth wheel, you only need 2 weighings:
1) Truck + camper
Reference: Learn To RV: How to Weigh a Fifth Wheel Camper (at CAT Scales)
For a travel trailer, you need 3:
1) Truck + camper w/ WDH engaged
2) Truck + camper w/o WDH engaged
Reference: Learn To RV: How to Weigh a Travel Trailer
After the first weighing, I then drive off the scale (forward, not backward) and make whatever changes I need to in the parking lot where I'm out of the way of everyone. While that happens, my wife goes inside and pays for the first weighing and gets the weight slip. Once she's back and everyone is in the vehicle where they were the first time, THEN I pull back onto the scale.
After the second weighing, I again drive off the scale (forward, not backward) and do the needful. Just remember, all weighings need everyone in their same seats/spots for consistency.
I've read about folks here unhitching on the scale and I've also read about scalemasters telling people to NOT do that. In fact, I believe I read a CAT scale sign that said don't do it. When I need to unhitch, I park the setup in a truck parking space or wholly off to the side somewhere it's not in the way. (Truthfully, this is the most nervewracking part for me.)
Once I have all of the numbers, I plug them into my other site:
Actual Weight Utilities - Towing Planner