An intruiging question. I am mostly self-taught with respect to instrument flying, formation , formation IFR, aerobatics and formation aerobatics. Not the easiest way to do it, but when there's no one around to teach you ...
I have learned most from pilots that have not sat beside me for hours, but rather the ones that I watched fly, and (unfortunately rarely) read what they wrote. This list would include:
Bob Hoover (read "Forever Flying") - met him briefly at OSH. The stick & rudder god. We are not worthy.
Andre Lortie - leader of the Northern Lights. Really sensible guy, and taught me about gates, which kept me alive (sorry, Transport)
Jim Leroy - incredibly aggressive Pitts solo airshow pilot - see
http://www.bulldogairshows.com - emailed him a few times, taught myself real end-over-end tumbles from watching the videos on his website over and over in slow motion, observing the flight control deflections.
Mike Goulian - author of "Basic Aerobatics" and "Advanced Aerobatics" - superb textbooks. Not perfect, but damned good. What a nice guy.
Patty Wagstaff - learned from her how to deal with elevator control failure, which came in handy later, after mine got jammed by a coax T connector, and I had to land with the trim.
Bobby Younkin - like Bob Hoover, he was a stick & rudder god that devoted his life to perfection in aviation. He really showed everybody what you could do with a "normal" airplane like an old Beech 18.
John Mohr - a very unusual combination, an intelligent pilot. What he does with a stock (220hp) Stearman has to be seen to be believed. He flies the wing, not the engine.
Sean "Pull the D Ring" Tucker - watching him showed me just how hard you can fly a Pitts - at least, one with Steve Wolf wings.
Skip Stewart - another Pitts airshow pilot that flies very, very hard, and incredibly skillfully. He's the guy that flies knife-edge under a motorcycle
Freddy Cabanas - taught me how to fly a Pitts S-2A in Key West back in 1990. What a guy. Somebody needs to write a book about him.
Charlie Hilliard. Another rarity, an intelligent pilot. Leader of the Christen Eagles. Famous quote: "the art of the solo airshow pilot is to aim at the ground, but to not hit it"