ALWAYS get a job before hand. Even if you have qualifications it's way easier to get it in advance, and you aren't guaranteed a job just because you've worked in said industry. I've seen people get a visa and move to another country and strike out on jobs at the mountain or mountains near them.
My british friends worked the Northern Hem season through a company that hired out for those jobs. I think there was a UK based recruiting dealio for it. But one of my friends did a few seasons. I think he's working in Europe now though.
Ask around and see what you can find out about searching for opening. Not sure if you can just find them online but check resort websites as well. I would not show up right before the season to wander around and try to find a job. At that point if you don't get it, can you afford to live without working there. Can you afford a pass if you aren't working at a resort. Would you be down to take another job at the mountain as a liftie etc to have some sort of work?
Lock the job down in advance, then get the visa and make the trip happen. They def seem to have a pretty big market for foreign instructors, but i would still lock it down in advance to be safe. Then you know where you're working, can start looking into accommodation etc. Even if you don't have a place to live worked out, you have a job and a general area of where you'll be living. IT's just a lot easiers at least imo.
Good luck always wanted to do a season in Japan, but not down to teach anymore. I still haven't found any good options for park jobs there. Maybe someday.