I found it difficult to maintain the state at first too. I did have to PR shorter sections of a book. I'd know I was losing it when I started to feel frustrated. When that happened I'd just take a break for a few minutes or try to get back into state depending on my mood.
For page turning I find it helpful to tilt the top of the book toward me elevating it a little. That causes the pages at bottom edge to step just enough that I can grab one of them with my finger. I suppose you could also press on the pages on the top right corner with your right hand and turn pages with your left hand for the same effect.
