Cant Sculpt

Hope anyone can help, its my second day with this program and i have been following a video tutorial on sculpting. i have followed every step but when i come to applying the brush nothing happens. I now it must be something simple.

Turn airbrush on and strength up, use subsurf at max,. Click and hold on your mesh and drag all around your mesh. And something will happen.

still not working any other ideas?

Do you have Layer enabled ?

I think so, I can see the object i am trying to sculpt. Do i need to press a keyboard button whilst using the mouse?

On the Sculpt panel:-

Try it without; failing that do you have enough vertices and a large enough brush ?

I tried that thanks but still no effect. This is driving me crazy