These are a few things that I have done over the years as a pianist and they have worked well to improve my technique and keep dexterity and fluency in my fingers.
One of the most critical things you can do to improve your technique is practice it consistently. In other words, practice every single day. Do not miss a day. Even if you can only play for five minutes, do not miss a day.
How Much Technique
If you have two hours to practice daily, start with the idea of one hour of technique practice per day. The second hour spent on actual repertoire makes sense toward decent progress. During your piano technique practice, incorporate scales, etudes and other exercises such as those found in a good Hanon exercise book.
Scales, Accents and Varying Accents
Start learning all major and minor scales in 4 octaves. Play around with the rhythm patterns of the scales. For example, try playing a scale using the rhythm pattern of straight quarter note rhythms. Then accent the first beat (quarter note) as you play all four octaves of a scale. Then play the scale again (or another scale) as you alternate the accent to the second beat, then to the third beat, then the fourth beat as you play through each scale.
Use Varied Rhythmic Patterns
Use alternating rhythms; i.e., play your scales using the rhythm pattern of a dotted eighth note followed by a 16th note. Then switch to the rhythm pattern of a 16th note followed by a dotted eighth note. Then try an eighth note followed by two 16 notes. Then reverse that to two 16th notes followed by an eighth note.
Use Varying Accents
For each of the previous rhythm patterns, place an accent on the first note of each pattern. Then alternate the accent to fall on the second note of the rhythm pattern, creating a syncopated feel. Then, accent the third note of the rhythm pattern, and so on.
Try using a triplet rhythm pattern, placing an accent on the first note of each triplet pattern. Then accent the second note, then the third note of each triplet pattern as you play a four-octave scale.
Choose some of these varying rhythm patterns for your four-octave scale practice. Use a metronome at a very slow tempo and focus on very clearly articulating each of those accented notes within the rhythmic patterns with relaxed hand placement and curved finger-tips. As you get more fluent, speed up the tempo.
Another idea is to use the above rhythms and accents at the same tempo adding dynamics. For example, start your scale at fortissimo and as you play your scale going up the keyboard, decrescendo until you are playing pianissimo at the high range of the keyboard. Then reverse those dynamics.
Or play the entire ascending scale passage fortissimo then alternate when you descend by playing the entire descending scale passage at the dynamic level of pianissimo. Change the dynamic levels to whatever you’d like, incorporating crescendo, decrescendo, piano, mezzo piano, mezzo forte, forte, and so on.