This glitch is old for me, idk if it is really a glitch but it's different. Alright first go to downtown. Since, i cant cap it then i'll have to give you directions. When you first start out, you are on a road. Go straight and then turn right. Keep going straight untill you find the little hole where you go to East L.A. You should run into a ledge w/ a rai above it if you go straight. Now grind on the lower ledge where the kickers are. When you get to the end, (where the above rail goes up) wallride the rail above you. This should cause you to wallride on both sides of the rail really fast. You can't stay on forever but its a start!

Yeah... just grind the "above" rail and hit R2 at the right place.... It's easier that way