This first part focuses on your control as you go from 16th to 32nd notes. This will switch your leading hand every quarter of the measure. If you have trouble with the combinations, play a measure of straight 16th notes first (to orient yourself) and then start these measures below. Repeat each measure individually until you feel comfortable if you need to, and then play them in order.
Next, we will take the same concept but focus on speed by increasing the 32nd notes within each measure. Again, feel free to repeat each one individually until you feel comfortable and then play them in order.
In this next part, we are going to extend the previous section by holding out the 16th notes longer.
Consistency is key to getting results here. If you give these exercises a chance, they can do wonders for both your hands and feet.