I haven't tried that particular recipe, but it is very similar to the one that I make.
As to draining the cheese, I drain and flip the cheese at the same time. I just tip the pot over, catch the curd on my palm, lift the curd to allow the whey to completely drain, then place the turned curd back on the bottom of the pot. The curd doesn't actually leave the pot. In my recipe you drain and flip every 15 mins to keep the curds evenly heated. As the curds have knitted into one mass, it should be very easy to just flip over the whole mass. Don't break the curd into small pieces. The curd is cut into small strips for spinning.
As to the ph of the curd this is critical, and personally I have refused to make another mozz without a pH meter. I have used pH paper strips, but they are too inaccurate, and sometimes I hit the mark perfectly, and sometimes I miss, and I too don't know whether the pH is too far, or not far enough. Ebay has some pH meters, or a local brew shop.