I actually did 6 of those shops (3 pairs), and they were not difficult. It took me an average of 15 minutes in each location and about the same on each report. I used a scenario that I was "buying new 4G phones and plans for my family for Christmas", effectively playing the technophobe mom looking at 4G "clever" phones.
The goal of the shops is to determine if you're denied any of the plan options, additional lines or charged an additional deposit based on your credit rating. All that's required to submit with the shop reports is the front page with your name and the "big number" that is your FICO score, with everything else blacked out for yourr privacy. I got my FICO free from one of the "big 3" credit reporting companies. I wouldn't use the MSC's recommended source for the FICO, because they're not one of the actual reporting companies, advertise heavily about identity theft, and I didn't trust that they'd be held to the same confidentiality standards.
The cell phone locations don't get to see your FICO at all, but in each case, I floated my number to see if they thought it would affect the cost of the plans I was offered.
I don't believe my personal/financial information was compromised by doing these shops.