You need to relax your hands, so keep hydrated and fueled up with good energy foods, do some stretches, warm up and practice in short sessions...do not do long sessions.
Simple exercise to feel how to speed up your play is to feel how your fingers work.
Set a tempo on a metronome, say 60 BPM, and with only one of the fingers you use play it on the beat......you are now playing BPM and you are playing 60 BPM as 1 2 3 4 1 2 3 4 1 2 3 4 etc.
Now with doing nothing more that adding the other finger you wish to use in between those beats, so now playing the "&" as well gives you 120 BPM as
1 & 2 & 3 & 4 & 1 & 2 & 3 & 4 & etc but feeling 60 BPM
This is important because your thought process is not hurried, you are playing more notes so the effect is faster but the tempo is the same.
In reading/playing these changes in speed occur, but the tempo remains consistent...it does not speed up or slow down.
This exercise will let you play 1/4 notes at 60 BPM, 8th notes at 120 BPM, and if you want 16th notes at 240 BPM all within the same tempo.
I always try to teach the importance of subdividing tempo with a Nome...not have it dictate to you....let it give you tempo/feel to play to not BPMs.
Repeat this process with any tempo, or sub-division to help you develop your technique, the beauty of this exercise is you think slow, so feel slow and then sub divide the feel. Rather than compete with the metronome, use it to play along with.
