It would be a good idea to blow any liquid out of the beer line. Using the CO2 would be best, but air would work also. He could use what ever cleaning kit he has with the canister empty and pump or squeeze air through the same as he would cleaning fluid.
If he using a pressurized tank for cleaning he could pressuize the empty tank and hook the coupler up and blow CO2 into the line from that end.
Remove the faucet and screw in a plug like this:
http://www.micromatic.com/draft-keg-...id-MP-070.html This will keep critters from moving into the line.
Unplug the unit and place an open box of baking soda inside.