Arousal control is arguably the most important factor for controlling prejack. Most prejackers are already at the end of their rollercoaster during kissing or foreplay, and they reach the point of no return immediately after penetration.
Practicing arousal control from the very start, before you even think about sex will instantly make you last longer. If you notice your arousal taking off you need to stop, bring it back down, and start again when you're calm again. You can practice this during training or during sex with a partner.
Don’t let the urge to ejaculate take over. If it does, stop all stimulation. Bring your arousal right back down, and start from the beginning of the rollercoaster.
Imagine yourself on the rollercoaster. On a scale of 1 to 10 the excitement stage is 1-6 and the plateau stage is 6-8. You want to control your arousal so you can stay within that 6-8 range.