i am a professional painter but im no binding/ski painter.
i suggets you use oil based paint, it dries much harder and has better bondage.
primer is a good idea, do it. also oil based.
sanding dose not have to be hardcore, just thorough, sheen must be broken everywhere, use fine grit sandpaper.
i assumer you are planning on using spray paint. i suggets using a roller, or back rolling (spraying then rolling while its still wet) the roller will help the paint penetrate into every little groove you made with the sandpaper, you can get a small roller (wizz roller) this will be easier than using a big one, and get fine finish.
there might be paint thats desinged to withstand extreme cold temperatures, if there is, get it, im not sure if there is but at the very least dont use interior paint (duh!).
Also be carefull not to paint the binding shut, this could happen if your all sloppy n shit. to avoid this use an exacto knife to break where it would dry the peices together while the paint is still wet. dont overdue the paint in general, for something like this multiple thin coats is better.