There's a special pda that is only for comp shop. You need to log into it with your TM number and workbench password to download the shop, under "Transmit". Then, you need to log into the shop with your TM number and the password "comp".
I never have any trouble with my Walmart people. Some of them actually like to chat with me while I'm working.
Be aware that the comp shop metric is weird. Any prices you enter after 70% of the total starts dinging your score. Apparently corporate thinks if you find more prices than that, you're pencil whipping it or not finding the right items. I was frustratingly red for a good 6 months before figuring that out, but now I'm always green.