I have to say I only used this method once - just to check if cheese making was going to be a hobby that lasted long enough for me to spend money on some moulds. Well, obviously, the answer was positive, and the next make was with a cheese mould.
About smoothing out the bellybutton ridges... I think there would be two options; proactive smoothing by placing something under the knot while pressing... maybe a smaller piece of cheesecloth or something, that would even out the wrinkles of the knot on the surface of the cheese... or reactive, as in cutting of the ridges or smoothing them out in a similar way as brine-washing unwanted microflora... I've noticed that brine/vinegar washes soften the surface so that it is easy to rub them smoother, while removing that unwanted microflora at the same time. Wouldn't do this before needed, though...
Waxing might make the whole smoothing thing unneccessary...
Somehow I like the proactive method more. You might also want to look into getting the knot as neat as possible. Twisting makes a larger knot than tying with a separate thread or so. That version of twisting that is in the east-european-woman-video earlier in this thread, seems to be pretty handy too. By twisting the knot to cover the whole surface area, you get a larger, relatively even follower that presses down the whole cheese surface, not just the knot-place. So I would imagine it to create less problems.
I would imagine that the wider twisted knot -thingie in the video would also help in making a larger surface to balance the weight on more easily. The weight in the video might also be easier than to think of balancing some kind of system on top of the cheese. But if you have a press (unlike me) then I guess it's a more press-specific question.
About other cheeses - I would assume that any cheese goes... just make sure your ball is in such a size that the knot/belly button doesn't go through the whole paste (create a hole in the middle). I'm sure this depends a lot on the toughness of the curds, but also the size of the ball or knotting method.
