These exercises can be done with the thumb or finger /s. Since a lot of pressure needs to be applied on the key spots of the sole, the thumb or finger soon tires and its joints start aching, but this can be avoided by simple exercises to strengthen the hands.
Exercise 1: Stand in Namaskara pose. Firmly press the palms against each other for 10 counts. Repeat ten times.
Exercise 2: Keep the finger tips and thumb tips of the two hands in contact. Exert pressure on the fingers and the thumb of one hand with those of the other for 10 counts. Repeat ten times.
Exercise 3: Forcefully bend the fingers of a hand backwards for a few seconds. Repeat ten times. Repeat this for the other hand.