I would not assume the hot water tank is empty if the freshwater tank is. Without the inflow of water pressure, the water in the hot tank will not be forced out.
To winterize I drain the hot water tank after the freshwater tank is empty and then put a couple of gallons of RV/Boat antifreeze in the fresh water tank
. Then rig a temporary bypass for the water heater and turn on all faucets one at a time until the pink antifreeze is flowing. Turn on all the washdowns (if any) in the same fashion. In the spring I hook the water heater hoses back up. You use less antifreeze if you do the faucets that are farthest from the pump first, then work your way back. Also, make sure the flow is the same color as the antifreeze in the jug to make sure you flushed the water that was in the hoses.
For the head we get a final pump out and then pour the antifreeze into the head and pump it through. You only need about a half gallon.
For the engine
, drain the muffler
and then take the raw water
feed hose off of the through haul. Put a couple of gallons of antifreeze in a bucket, put the raw water feed hose into the bucket and start the engine. Watch for pink antifreeze to some out of the engine exhaust
port, then let it run for a few more minutes (but don't let the bucket of antifreeze run dry), then hook the hose back up to the through haul.
I am not sure if the air temperature gets below freezing where you are so I can't comment on whether you need to winterize the systems or not. If you need to, this is how we do it every year.