I have looked at many tutorials, and tried them, and they have never worked!!!
All that comes up in the UV Image Editor window is a flat silver colour, covering the unwrapped faces.
EDIT: Whoops, wrong forum, ahh well, I shall be moved:).
i had a lot of trouble too, but i used render backing, witch is more or less the same way, i beleive.
Unwrap a cube. Add multires up to like 3, then duplicate it.
Make the duplicate (D) up the fiftth multi-res level, for example, then sculpt it around, so you get some diffferences (probably not necesary in render baking). Go to your first cube, unwrapped, and do image, new. now go into render settings window>>bake settings>>then whatever. i’m not sure what options you choose, but for normal mapping, i do tangent, cause i’m supposed to.