keeping it clean

what does everyone use to clean off the scumm line (dull build up) after leaving their boat in for a long weekend. I want something that works to remove grim but is real safe on gel coat.

3M Hull cleaner from Wal-Mart. I put it in a spray bottle - squirt it on, wait 1-2 minutes, rinse off with a hose - maybe a VERY little scrubbing in some spots - usually none required. A lot of people say toilet bowl cleaner will work just fine and won't harm the gel coat but after reading the label, I haven't worked up the guts to squirt that stuff on my boat...