I recommend talking to the nurse about the clamps, especially your question on using two at a time.
My gut feeling is that its probably best to alternate clamping, but the techs are rushed and will do both sides if you don't request otherwise. This document says it should be one side at a time, but really they should be held:
http://www.therenalnetwork.org/qi/resources/VA_Solutions_Staff/11.ClampUsagePolicyandProcedure.pdfPolicy:
Using clamps on new or underdeveloped fistulas is prohibited.
The use of clamps post-dialysis to hold sites for mature fistulas and grafts should be restricted. If and when clamps are used on a mature fistula or graft, use one clamp at a time to prevent excessive pressure/thrombosis. Patients and/or family members should be instructed to hold sites, and if this is not possible, staff should hold access sites.
I was always told that clamping is bad for the fistula and will make it have problems much sooner. But I could hold both bandages fine and was interested in my care. I'm sure they didn't tell that to frequently the 80% of the people in the center who were using clamps, even people who probably could have held their own bandages.