i've taught more players than anybody. i could teach you this or that, but i could also make you good in a few weeks. But for that I would have to charge you.
my most successful student is LoNe
LoNe used to be so good he could 1v2 me and swift, it was insane.
other than that, i wouldn't recommend you learn from anyone other than shotgun. He's better than me, but not a better teacher.
I think I'm a good teacher because I've done it so much that people tend to have the same issues, ask the same questions, make the same mistakes etc. and i can easily tell what's occurring and correct it. Other players can do it too, but I don't think they can get inside people's heads to understand their perception of what's in front of them. That's what I'm good at in general.
Vizzer is decent, but I don't think he really understands too much about the game at a competitive level.