Cathy,
I usually hit those places more for the salvage items than for the bulk items. For example, if I can get some Smucker's preserves for under $1 as opposed to $3-4, I am a happy camper.
I look for deals. Once I find one, I quickly assess what I will do with it. For example, while in Cleveland, I would occasionally visit the Stouffer's plant salvage store. They needed to get rid of cases of the Nestle foodservice pack 4-5# Macaroni and Cheese. They offered to sell them for $5 a case. I asked them for a discount if I would move 50 (yes, 50) cases for them. For $200, I scored 1000# of Stouffer's Macaroni and Cheese. And in 4 hours, I was able to able to get rid of all of it.
Hit Eastern Market in Detroit late on Saturday afternoon during the summer, and you will find case lots of various vegetables for $1-3. My Italian neighbors in Dearborn loved me. They would have a great stream of vegetables coming from the Market FREE, and all winter, I would have little old ladies bringing their cookies, panettoni, expresso, homemade sausage, etc.
Storage and planning are critical. Also, finding a store that keeps the product FRESH is also critical. Some of the worst bulk places were the Cleveland major grocery stores (FINAST comes to mind.