RE: any winter stuff that helps windsurfing
For me the best winter alternative to windsurfing is windskating. You put a small sail (about 4.5m2) on a skateboard (you have to attach a base to the skate - drill a hole in it). Go to an empty parking space or a basketball field or something and try it. It's really fun you can do all the moves that you could do with a windsurf. If you want you can put footstraps on the skate but i don't like them because they increase the chance of injury.
Also just snowboarding is good. Just try jibbing around, like doing 360 spins on the floor or you do like an 180 into a nosepress and then another 180. It's great freestyle practice.
Or you can build a windskate and take off the wheels from the skate and add some metal blades to the front and rear end of the skate. That way you can ride it on snow.
I've also seen people using skates with a ''big foot'' ski under it and riding that.
Whatever you do, be carefull. Snow and ice can be dangerous and if you get hurt and break something (like i did) you could end up watching other people windsurfing in the spring. So I strongly reccomend you to get a helment and some protection for your back. If you fall, keep your hands close to your body and avoid falling onto them if you don't want broken wrists.