Its easy! Get your water. Test the pH with your tester. Add pH up or down depending on if it is high or low. Mix vigorously. Test again. Adjust again. Mix again. Repeat.
3 or 4 is all you need. Honestly if you keep adding more holes you reduce the structural integrity of the cup. Here is a post from the guy that I follow the most.
I would go there and look at his journal as he is a good guy to emulate.