I have only done it twice myself, but it worked so well the first time I now permanently keep two wadded-up shopping bags in my pannier in case I get caught in the rain. With a snug tie around the ankles, water did not sneak down into the shoes. Depending how long your socks are, you might have to push them down.

I did not experience chain-suck. If it did happen, I'm pretty sure the bag would be weak enough that it wouldn't matter -- you wouldn't be stuck or anything, just tear away. But then you lose your water seal, so it's probably good try to sitchiate things so that the inboard side of the bag is more taut, and any flapping is to the outside.

And of course, this solution is not for everybody. You have to be pretty secure with your inner Fredliness to ride around like a homeless person.