any kind of wax work, candle is fine... parrafin is a good all around wax for all sports involving rails... (rollerblading skateboarding biking skiing snowboard fuckin scootering etc...)
u can get like 4 nice size bars for like 2 bucks at your local grocery under the name "Gulf Wax"
No you can use surf wax on skate rails it works fine. However, because it is so dirty and the grit will get in your bases and dirt sticks to it. Candle wax is good. Ski wax works great. My opinion is swix ch12 or cheap warm ski wax