That little bit of left over water in the bilge at the end of the season can cause problems. It doesnt take to much ice to crack the base of your bilge pump(s) if water is left in there (believe me, I learned the hard way).
Cut a 12" piece off and old t-shirt and push it into your bilge drain hole with a screwdriver. Leave 4" hanging out the drain. The water will wick its way down the rag and out the bilge.
Works great for you guys on blocks. Trailer guys remember - no matter how high you get that trailer tongue, the drain hole is still 1/2" above the bottom, water will not drain completely.
This sure beats dumping antifreeze in the bilge and is a heck of alot cleaner