+1 on the confirmation marking after a turn. Also note reasons for caution like rough pavement or the need to slow down on a downhill prior to a turn.

But I've never actually done route marking so I can't help with anything else. I've wanted to help out with it but my club always does it on weekdays when I have to work. I would bring a cooler for cold drinks and plenty of snacks, because that's something I always bring when I'm going to be the car for a while. Also Wet Ones if needed to clean up along the way. And plenty of good music to play on the car stereo.