I stopped using muffs because I'm always working alone and they have fallen off or leaked so bad that I hate them. So I use a huge plastic storage tub that I slide under my Bravo drive. Then I fill it with water and just keep the hose running on a trickle. I feel much safer that way while I'm on the boat not able to watch the hose.

Yup, I use the pink stuff. As far as the t-stat, I just made sure the motor was up to regular operating temp. My current (525efi) and last motor (496HO) had closed cooling so no worries about the t-stat.

I run the pink stuff through, and then drain everything. I always drain my headers after I flush even during the season. I read that draining them prolongs their lifespan.