The first time I used the CAT scales, I was also intimidated, for the same reasons you cite.
But it was super easy, you literally just drive on, they weigh it, and you drive off. There are separate platforms that each axle set - tow vehicle front, tow vehicle rear, and the trailer's axles together - so you get individual readouts, plus the combined total.
Pull onto the scales very slowly, and drive off slowly.
They're like giant scales, and they wiggle around a bit.
The scales I've been to, when I initially pull onto them, I got out and spoke to the attendant inside - that's their procedure. I don't know if they're all this way.
Once you've got the first one under your belt, it's a piece of cake.
'07 Ram 5.9 QC/LB SRW
Full
Carli Suspension
35" Toyo's | 4.56 | PacBrake
2009 Cyclone 3950 | B&W Turnover Ball & Companion | TrailAire | Duravis R250s