a) who thinks it is a good idea? - Yes, if it needs done, definitely
b) who has done it and if so how? - Something like below (if it works with shorter focal length lenses)
I personally wouldn't bother. The depth of field on a macro lens is so razor thin anyhow, I usually just set focus to closest-possible and then gently rock towards or away from the subject until it looks right in the viewfinder. Just me.