Your mind probing questions are formed from your postview and trigger words you wrote down. If you're not writing down trigger words during preview or postview you are not really giving your mind anything to get curious about. If all else fails turn the subheadings into mind probing questions.
You never would use a new tool without testing it on a few scraps before applying it to your work of art where you only get one chance to get it right. You test the tool what it is capable of on scrap material and only when you are confident that you can handle the tool well enough do you use it for that masterpiece.
PhotoReading is a reading tool it gives you more options.
Technical books for your studies is like working on a masterpiece. Don't start on them until you have learned the system on some lighter material of about 250 pages (non-fiction). Don't learn something new on your important masterpiece. sitting. Learn PhotoReading away from your studies first. Once you know how the system works apply it to your studies.
A technical book should be handled the same as textbook. Treat each chapter as a book in itself. (yep it does mean more of the book is relevant but still only 4 to 11% of the text carries meaning.)
Alex