I just got done winterizing my R21-EC. First time for me!
First I ran the tap until the fresh water tank was empty. I poured 3 gallons of the -50 Non-Toxic Antifreeze through the deck fill port, then ran the tap again until antifreeze came out the tap, then out the external drain.
Next, I had the black/waste tank emptied, closed the seacock, then poured 3/4 gallon on the antifreeze down the head, flushing away until it was only antifreeze. I also poured the other 1/4 down the external pumpout into the tank.
I poured two gallons of antifreeze into the bilge, directly and through some of the drains. That's enough to get the pump going and get out any water.
I pumped out the oil and changed the oil filter now instead of spring. It was recommended to me by the surveyor to do this now so I don't have to deal with it in the spring. Totally optional step.
I filled a bucket with fresh water, then connected a short length of hose to the intake connector on the starboard side of the engine and dropped the other end in the bucket. I started the engine and ran it to flush out the salt water for awhile (I've heard of people adding some "salt-away" solutions here), continuing to add fresh water to the bucket. Then I dumped the fresh water and poured 3 gallons of antifreeze in the bucket. I ran the engine until it was all about gone and coming out the exhaust. I dumped the rest in the head.
Then I disconnected the batteries and brought them into the garage. I used some zipties to keep correct wires together.
I removed the radar dome from the mast so I could disconnect the wires, then removed the mast. Both are laying on a mat on the bow with the anchor.
Finally I pulled my slick new cover from Fisher Canvas over and we're good until Spring!
Edit: Forgot to mention that I filled up the fuel tank on the way home from the marina, and I added diesel fuel winterization additive.