Amazing spread of experiences on such small a subject
. No wonder, that packing lists, footwear and rain gear are constantly discussed subjects.
Anyway, my setup is two "Large Rectangular Dry Bag" (14 liter/34 g) and a "Food Dry Bag" (14 l/43 g), all from Zpacks.com. One "Large" each for clothes and for sleeping gear. I could get away with useing smaller bags on the Camino, but the weight is negligible, so I don't bother. I also use a smaller no-brand silnylon dry bag for my poop-kit. The food bag and the poop-kit I don't bring on the Camino. Inside the clothes bag, I use small stuff sacks (also from Zpacks, 3 g each) to keep things organized. Plus a small stuff sack for my toilet gear and one for miscellaneous. I keep a few things, like my phone, memory cards, repair kit and my soap bar in Ziplock bags. Makes for a very organized pack that packs tightly. Some times I use a trash bag as a pack liner slash keep-the-bugs-out cover for the backpack.
If you are on the market for dry bags, then keep in mind that not all of them are alike. My current cuben fiber 14 liter "Large" bags from Zpacks weigh 34 gram each. My older 12,5 liter dry bags from Karrimor weigh 93 gram each. But I can get three Karrimor bags for the price of one my Zpacks bags.