I definitely prefer to PhotoRead material first, but it really is a personal preference. Explore it both ways.
Many people have said that following the 5-day plan curtails over-dipping. You see, one of the goals is to get the entire book super read and dipped within the 30-minute period.
Unless it is a small book, you cannot over-dip and still get through the book.
When you do the process over several days you learn that you get the book in an incredibly short period of time without over-dipping.
There is nothing wrong with over-dipping if you have all of the time in the world, or if you are curled up some evening for pleasure with a book. But, when you are looking to zip, learn, and go on with your life, then...