my skatepark is sooo sweet, we have like 3 ledges that are super smooth, and are always waxed really good, and we have like 3 rails that work really good, and its all kinda sloped so you can get speed. but to prep a ledge id say just get some big candles and just wax it really good, it would only take like 5 or 10 minuites, then if its cold enough throw some snow on there and bring some water bottles and spray water on the snow, then put on another layer of snow on top of that and wait like 10 minuites, then scrape it down to get it even.