Hi!Is it good to use hand grippers beside finger exercises to build up finger strength? Or my fingers might become stiffer or something?
The best way, again IMHO, to get there is practicing... up to the point that your arms might be a little tired, but not much beyond. Other finger agility exercises can help too
"Agility exercises" are intended to "develop speed", which is the wrong mindset and has caused lots of sorrow to many generations of piano students. Instead of striving for speed, which is already inborn, we should be learning how to SLOW DOWN, create awareness, and practice the "Music of Silence" (free after A.B. Michelangeli). That is how you unlock speed.