Instinct tells me not to hang your bike by the wheels. Rather hang the bike by the saddle and the stem, something similar to the pic (the red dots are the hooks). That way you are staying away from the frame and won't scratch the paint. Problem with hanging a bike against a wall is that the pedal and handlebars get in the way, and that the bike then hangs at an awkward angle. Remove the front wheel, turn the handlebar away from the wall, and then have a hook on each side of the stem, together with the hooks under the saddle.
If you do decide to hang the bike by the frame, cut up an old tube and pull it over the hooks for extra protection.