just take it slow and gradual and dont expect too much from yourself at first but also dont be afraid to push your limits. Also u should be doing forearm/finger/hand/shoulder/neck/basically any upper extremity stretches those will help a lot. Look up Dr. Levi Harrison for some good stretches
That keybind seems it would be hella uncomfortable after doing 2 + 2. Either way, you just need to build new muscle memory. Just playing songs between 20 - 30 and trying to AAA would probably be a good start.
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