I have never really practiced to increase my speed. But I guess you'll get a lot of results if you only spend practicing scales with a metronome to increase your speed for 30 minutes per day.
One of the result would be carpal tunnel syndrome I think, and also, being unable to play something in a solo that wouldn't sound like an exercice.
But I think you could increase your speed by 60 BPM in a month, but then, you wouldn't go farther for a while. You'd have to play something else, then come back to it.