Alekhine
If you could train on the hands of a dead chess player ! who would you choose?

That's tough to say because there's no guarantee a great GM or IM would necessarily be a great teacher. In fact they might be much worse for most of us than a "lowly" FM or NM who was an excellent teacher. AND being an indecisive shnook it's tough for me to come up with one choice only!
BUT, to finally answer your interesting question, I'd choose a GM who spoke english (since I'm not bi-lingual) and who I think I'd get along with in general so I might pick the late GM Mednis who I met (and played) in person once he seemed to be a nice guy and he wrote endgame (and other) columns for CL for many years that I enjoyed reading. In case he wasn't available I think GM Euwe might be a good teacher as he wrote lots of instructive books and was once described by Fischer as being "too normal" I think I could deal with that a lot easier than someone "too crazy" like Fischer!
If you could train on the hands of a dead chess player ! who would you choose?