He did write a book called It Is Done! The Final Step To Instant Manifestations that contains an old letting-go process, that I've heard described from other sources as well.

Here is an excerpt from that book.

Find a quiet spot / place where you will not be disturbed for the next 5 to 10 minutes. Initially, it helps to find a private spot where you can do this exercise without any fear of being interrupted. Make sure that the spot is just right and comfortable for you, and remove any distractions from the area.

Close your eyes and take 3 deep breaths. Breathe in deep and feel the energy flowing all over your body. Feel the good feelings and sensations as you inhale deeply.

Breathe out slowly and with each exhalation, feel yourself becoming more and more relaxed. Know that you are becoming more and more relaxed.

After taking 3 deep breaths, proceed to visualize your desire or state your intention. (At this point, you can do whatever manifestation practice you usually do. I will describe my practice in the next few sentences.) As you do so, form a mental picture in your mind about the desire already fulfilled. For example, I saw myself queuing up to collect my prize after I played the game. I also felt the elation and happy emotions as I was queuing up to collect my prize.

Take as much time as necessary at this step so that you can feel the emotions clearly. As you do so, tell yourself that it is happening not in the future, but right now. Feel your desires coming true and happening for you right now, at this very moment, and not at some spot out there in the future.

When you have visualized everything to your satisfaction or stated your intentions to your satisfaction, say “It is done!” silently to yourself and feel the “It is done” feelings peaking. I find it useful to repeat the phrase three times consecutively, saying it out loud in my mind firmly as a proclamation.

You can do all of that if you want, or you could stick your request in a box, or you can just make a decision not to think about it again, or you can distract yourself with something else until you forget about it, or variations on the same theme - all have the same effect of stopping you thinking about your request again so that you don't interfere with the original purity of it.