I believe strength=speed. The stronger your fingers are, the faster they’ll be able to go. But it’s completely pointless if your picking hand isn’t up to par and coordinated with your fretting hand. I’m finally making my finger exercise video tonight that contains exercises that will help with strength, coordination, accuracy and dexterity.
But here’s a thought to keep in mind:
It’s not all about increasing the speed as much as it is muscle memory. When I was struggling with increasing speed I actually noticed that the longer I played it for a slower durations, next thing I knew I was able to increase my speed and no time. For example: If you increase the BPM by one every single time you get it right, before you know it you are straining your hand and racing against the metronome. Practicing speed requires relaxation and confidence. Also your right hand has to change its method with how it approaches it. How you pick sixlets at 130 BPM is not the same as what you do with 8 notes at 90 BPM. So what I would suggest is play what you are trying to play consistently for a half an hour everyday at a very slow tempo WITH NO AMP. And then after a couple of days challenge Yourself by increasing the bpm by 20. This way you have the muscle memory and the strength built and then when you go to challenge yourself, your right hand will have to teach itself how to handle faster picking. You will slop it at first for a good while. But after a few tries your picking hand will start to realize what your right hand has to do to pick that fast. I hope this helps