With these in mind, the first solo masturbation exercise aims at learning to understand your arousal level and control it.
On a scale from 1 to 10, we consider 1 and 2 as your normal not aroused state, something you feel when you work or your house chores. Basically, anything not sex-related at all.

Stage 3 and 4 is when you first think about sex, and your penis gets slightly engorged.

5 and 6 are the stages where you definitely can feel the arousal, your penis is ready, but you still feel you are in control.

7 and 8 feel like being inside your partner and having a hard time shifting your attention to anything else.

9 is a pre-orgasmic state, you feel that your penis starts contracting, and 10 is reaching orgasm.
If you want a deeper dive into the theory:
Now, let's dive deeper into arosual control.
Start–Stop Theory
Hakima Tantrika
Sex, Love, & Relationship Coach, Writer and Educator
Certified Sex Therapist, Family Therapist
Natalie Goldberg
Cameron Fraser
Australia's Leading Men's Sex Coach
Dr. Justin Houman
MD, urologist and fellowship-trained Male Reproductive Medicine and Surgery specialist, UCLA whose practice is focused on men's health, include male hormone management, sexual and ejaculatory dysfunction
Stop-Start Method
8 is a risky stage, so take your time, cool down, breathe deeply, relax your muscles, keep your eyes open wide. Now repeat this exercise 5-10 times, so the total time of this practice is about 20 minutes. The longer you can do it – the better. Here, you are reprogramming your brain and muscles. You become a master of relaxing and getting aroused. You are mastering control.
Start the masturbation practice and get to stage 4 or 5, slow down, relax your muscles, breathe deeply, and open your eyes wide. That's a trick to distract your brain from sexual arousal. Notice mindfully how your arousal weakens. Listen to your body and learn which muscles you could relax and what you felt. By knowing all those details about your body, you will be able to identify and control your arousal. Lower yourself to stage 2 and start increasing the arousal again. This time stop at stage 6, come down to 2 again, and now attempt to reach stage 8.
Find a 20 minutes in your day when you are alone
Our suggestion is to practice this 3 times a week for 2 weeks.
If you slip down during these exercises and can't control yourself, no problem. Just take your time, be more attentive to what's happening, and you will learn all the minor signs that indicate that you are approaching orgasm.

Once you've mastered this one, you can advance yourself with a little trick.
At stage 9, when you feel that the point of no return is approaching, hold, squeeze your pelvic diaphragm muscles for 10-15 seconds, like you're trying to stop yourself from going to the toilet, open your eyes wide and breathe deeply. If your pelvic muscles are already strong enough, this will be enough to control ejaculation. If not, keep practicing. Another option is to squeeze the head of your penis for 15 seconds 2-3 times. Experiment and see what works best for you.
Text version:
For best results, please follow the video version:
Practice 1