When you beat classic mode on any difficulty go to LA then go to the fire truck then look over down the block where there are stores goto the one next to the green building go in the door you should see the word production drop.
Now go on the building next to you's top then jump on the highway now skitch a car going down the highway towards the carwash skitch it then jump off when it turns then explore.
You can use the white button to clean your combos but you can also use it in anther way. The first way is doing a combo and getting up to a ledge or a cliff, etc. One example is in Skatetopia. When you get 400 points and bet skatetopia you have a second part where you have to set all of the fireworksang one of them is the Fountainof Glory. This is one of the hardes of the fireworks. To turn it on you have to grind on the wire and be at top speed and you have to have special and when you get on the bar press the white button and when you get towards the top you jump towards the edge get off your board and grab the edge and pull yor self up. Then jump and press the grind button. that is how to use the white button and I gave you a little tip with it.