When you're holding the neck barring a chord, where exactly is your thumb supposed to be? I feel like it's the source of all my discomfort.

I brace it against the back of the guitar neck somewhere between my first and second fingers.

i generally use the classical technique. my hyper-mobile thumbs have made it quite easy for me to do.

forgy, do you own a E-H holy grail cathedral by chance?

I don't. I had considered getting one when I was looking for a reverb pedal last year, but I plumped for the more versatile Digitech Digiverb instead.

my guitar does the same thing, its mad annoying. try muting the E string with your thumb when you play chords. Also, i've been trying to learn some Grateful Dead songs and damn these songs are giving me trouble for some reason.

Alternate picking, sweeping, fingertapping, harmonics, (more) speed etc.

harmonics aren't really that important. work on your picking.

Tell that to Jeff Beck.

somehow i don't think quinn is going to be the next jeff beck.

i'd say good picking skills are much more essential than good harmonics. you have to learn to walk before you learn to run, that sort of thing.

I take the view that you should develop as many different techniques as possible so you can incorporate them into your playing style naturally. You'll become a much more creative guitarist that way.

I wouldn't say harmonics are less important than alternate picking, either, unless you really want to become a shred guitarist over anything else.

Well, for picking, are there any exercises/tutorials someone might have?

Try some curls.

there are millions of exercises out there, some as simple as just playing through scales over a metronome and gradually increasing the speed. you cant go wrong with learning actual songs though. cliffs of dover has some great alt picked parts throughout, just play it at your own pace until its clean, then gradually speed up until you can match ej (this may take the majority of a lifetime)