Wet sanding - the surface that you are sanding is wet, and rinsed frequently while you are sanding.
Coat, the way it is used here means that the CA glue is re-applied after it has dried and been wet sanded. So Glue, Wet sand, Glue again, Wet sand and polish.
I get a great edge just from sanding it then gluing it. Yes just once. Maybe these other guys are more demanding of a perfect finish than I am.
The spray is a Zap Kicker or other CA glue accellerant that is not applied to the chassis but to the Cardboard box that the chassis is placed in. The fumes from the accellerant on the cardboard make the glue on the chassis dry faster and voila. Hope that helps.