There are different shops that audit pet stores. The one most infamous provides the shopper with several pages of UPCs and product names. The instructions are to either (1) find the matching product and record the price if the item is on sale, or (2) find the matching product and record the price. Store employees need to stay out of your way while you work as covertly as possible, armed with printouts, cell phone, camera, DVR, etc.
If the store is small with less inventory, that makes it quicker to check for prices. However, it can make it more difficult to work discreetly. The assumption is that this is a competitor shop. In my opinion, it is not an easy shop. I've done only a handful of them, 2 different MSPs, at different locations. It's not a shop I would ever do again without a boatload of money.