I never had any interest in controlling the Master Hand and I actually had no idea it was an option! If anything I think I'd like to control his crazy brother. That was a fun boss to beat... Master Hand is kind of tame and should stick to doing things that begin with "master".
And welcome to Usagi as well!
For Melee, I don't know if they brought the glitch from Brawl however, you have to put your 3rd player hand in the name entry section, and hover over "Name Entry" rather than the names. Then on Player 1, as soon as you press start, press A on Name Entry for Player 3 and that's how you play as Master Hand. Oh and you can't have a player selected for Player 3 while doing so. :X