I wet skim and top off with salty water for my water change also. My skimmer cup has a drain to house sewage and my top off container has an automatic dispenser to add salt:
http://www.drsfostersmith.com/produc...6&pcatid=14436
I just added the Koi feeder filled with salt so hopefully it won't clog or rust.
I don't miss that 50 gallon Rubbermaid container that used to sit in front of the tank for water changes!