You would need to focus at the center at the very beginning. Once you relax your eyes without converging, you'll find the blip. To keep the blip, remind your eyes diverged and relaxed. It's my usual practice for keeping the blip always, from up to down, and usually 3 to 4 cm wide, depending on the size of each page of the reading material.
Using the blip is NOT the only way. It indicates you're in photofocus, and however using the imaginery X technique is useful too. Notice white spaces on book edges, and the 4 corners, would do the same job.
To see the success more quickly, I recommend using a larger-size book at first as the blip is normally bigger.
