When you said you used the "hot and low drain", do you mean you used the drain near the fresh water tank itself? My fresh water drain is very close to the bottom of the tank and only leaves about 1/2" of water in the tank. I know not everyone likes to do this, but I put pink stuff in the tank, too. It's not much, but enough to mix with the water in there. I run a lot of fresh water through the tank in the spring anyway, so it flushes things out really well. Easyride is right, though. There is plenty of room for expansion in the tank.
To pump the lines full of pink stuff, I used the method in my ('89 345 LE) manual. I disconnected the intake side of the water pump and attached a 4' hose that I put directly in the bottle. The pump sucks it right out of the bottle so it uses very little antifreeze to fill the lines. Of course, I bypassed the water heater. The pump has a backflow preventer, so I could reconnect the regular intake line without leaking antifreeze. I hope to permanently plumb in the antifreeze intake hose with a "T" and a couple valves so I won't have to disconnect anything next year.