Good friend, bad GM/Player, what would you do?

[Phhase]

If you haven't already, tell him that DMing isn't about telling your story. It's about giving the players what they need to tell their story. You just provide as many options as you can. For everything he wants the players to do, ask him to think of it from a player's perspective. What if they DIDN'T want to do that? What if they had a different plan of attack? Reward these things.

As for being a bad player...uhh...has he read any classic fantasy like Icewind Dale or Dragonlance? Short of just saying "dude you're a sh!t player stop being dumb" (Bad idea obviously), that's the only idea I have on showing him how things are "supposed to" be. That, or show him some select tales of DnD epicness, like the PalaDM. Just so long as he knows it's not about copying, those things should help.

Heck, the rest of you are good DMs or players, right? If you can, maybe he should just observe for one session, and take notes on how the structure of the game works. Hoe people react. Things like that. Outside perspectives can really help.