I did one and it was tough.
I was the only customer, so of course the salesperson was on my tail wanting to help me. I used a story that I was thinking of buying a phone for someone as a gift and just wanted to check out what was available. First, although it was 230 in the afternoon none of the phones were turned on, plus none of them had any signage indicating what models they were. So, I had to ask the salesperson to turn them all on for me so the models would come up on the screen. I went around and took a pic of every phone, then searched the pics after I left to find the models that were needed to upload.
You don't really need to be stealthy taking the pictures. Everyone takes pictures of everything these days, and I just told the salesperson I was going to get pics of what was available and go home and do some research.