I don't know what other people use, but to stack bowls I often will put those little Rubbermaid or Tupperware containers between the bowls. The bottoms usually nest in them pretty well.Bar Keepers Friend can be found at Safeway (at least around these parts they can) and King Soopers ( a Kroger store). Sometimes I have to look hard and it's usually tucked away on a bottom shelf somewhere but it can be found! If nothing else there is always Amazon.com.
I've found Bar Keepers Friend at Kroger, Piggly Wiggly, and Wal Mart. Empty tuna cans work well to stack bowls.
I actually use my small fiesta fruit bowls for most of my stacking. I got a ton of them for my wedding, and really never used them for anything. Now they have a very important purpose! I found Bar Keepers Friend at Target, and yes, you do have to look hard, it was on the bottom shelf for me too!
i could only find the Bar Keepers friend locally at Home Depot
You could also use florist green styrofoam.They come in differnt sizes and stay put.They are at a craft store. Elma email@example.com
i use the small tupperware containers and ramekins to stack mine. i also sometimes use the bowls i don't love so much to hide away and add height to my stacks.and if you can't find bar keepers friend, magic eraser works wonders on cleaing up pyrex too.
I use custard bowls. Bar Keeper's Friend is also sold at Bed Bath & Beyond plus you can use a coupon on it. The carry powder and gel version.