I bypass my heater for winterization so I save about 6 gallons of the pink stuff.
I got a piece of hose, fittings, and clamps, in the plumbing aisle at Lowe's. I don't remember what the whole thing came to, but I'm sure it was way less than $10. It's a 1 time investment.
I drain the fresh water tank and heater, blow out the system from the dockside water connection, bypass the heater, pour a couple of gallons of the pink stuff in the fresh water tank, and turn on each faucet until pink comes out of it.
After the system is winterized I reconnect the water heater so its ready to go in the spring.
The hole process takes just a couple of minutes once the tank is drained.
Use about 40 or 50 PSI to blow the system out. I think that's about what I get from the hose on the dock so I know its safe.
If you blow it out properly you can probably skip the pink stuff, but I do it just to be sure.