Here is my suggestion. When you arrive at the facility, do not go onto the scale first. Park and go inside and explain you are wanting to do three seperate passes over the scale.
Pull onto the scale and get your first weigh with your weight bars engaged. I use the last four of my license plates as my truck number
Drive off the scale, get out of the traffic pattern, release the bars, drive back onto the scale, tell him on the speaker it is a reweigh.
Drive off the scale again, go find a corner of the lot to park and disconnect the trailer, go back for a third trip onto the scale with just your truck.
Go inside and pay. I will likely be around $13 for all three tickets.
You now have all the info you need to determine your loading values.