I've just been practicing some exercises out of a Paul Gilbert DVD recently. I've been trying to incorporate some of the routines in to my practice schedule. What I'm up to is picking 16th note triplets at about 80 BPM (I've been playing for 10 years but unfortunately have put off metronome practicing until recently, unfortuately
This is exactly what I did two years ago...PG was the first vid I got into and I never used to practice with a mentronome! Not only that, I used to hold the pick like I was passing a joint instead of holding it like PG suggests in the vid. So you coulds say I started from scratch.Thinking thicker is better as far as picks, I went with the big stubby picks they're made out of Lexan and produces a mellower tone that the nylon Jazz III's. I scored them all with a knife and it helped some, but they still slipped. Eventually I went back to Jazz III's...anyway, I was having the same problem with the pick shifting as I did exercises. It still happens...though not to the degree it happened when I started and, like you, it happens when I'm picking for an extended period of time. I did two thing that minimized the problem:
1) It's been said that holding the pick at a 45 degree angle to the stings is the way to go. For me, this works up to a point. Once you get to a certain speed or a very long practice exercise, this causes drag. What I do now is hold the pick almost at a 90 degree angle to the pick (Shawn Lane holds it this way too...althought the vid was deleted on Youtube). Since I anchor my hand on the bridge, this is more noticeable when picking on the B and high E strings. So, on the low E string, it's about a 45 degree angle and increases to a about a 90 degree angle as I progress through to the thinner strings. This sounds like the pick changes the attack angle drastically, but I really didn't even notice it until I looked. It
almost at a 90 degree angle.
2) The second thing is that I only use the very tip of the pick and only enough force to get the sound out. When looking down, I look between the pickups and you don't see a lot of the pick dip below the strings. Sometimes I want to dig in for the tone, but most of the time I picture the pick as having wet paint on it and all I am trying to do is put a small amount of paint on the string.
I'm wanting to give the Jazz III- Max grip a try...
http://accessories.musiciansfriend.com/product/Dunlop-Nylon-Max-Grip-Jazz-III-Guitar-Picks-6-Pack?sku=582855&src=3WFRWXX&ZYXSEM=0&CAWELAID=435963376