In story mode go to Bevery Hills. In the little mall area there will be a ladder. Climb the ladder and you will be on the roofs. There is a huge wall and a little spiraling roof right infront of you. Go inbetween the wall and the spiraling roof and you will see the spriling roof leaves enough space to climb up it. Climb up and grab on so your back is facing the wall exactly straight and press the "Tag" Button. Don't hold it though. Press it so the arm moves and the let go. A constant stream of paint will be coming out of your hand and it looks like your hand is on fire. To get the stream to stop, just tag a wall.