You must experiment and see what works best for you. The danger is to get so pre-occupied with the PC squeezing that you lose the wonderful energetic connection with your lover. A bit of that is probably inevitable, but you will find once you discover your own method, that you can do the squeezing without distracting yourself from your partner. And, actually, you will get to the point that you can move the hot sexual energy without any physical squeezing at all, simply by placing your attention along your spinal column from the coccyx to the crown of your head. This requires that your body knows how to do it, requiring many skill set repetitions to attain.