In any sustainable growth and maintenance, nutritional diets and constant work are required. Think of your physiological muscles. You can pump to gain, but when you stop, you get muscle degradation and degeneration. Just like PE, gains need cementing and maintenance.
Bundle stretches is the go to active and aggressive method. I incorporated the bundle stretches into a semi active method with hanging as well while stretching my tight muscles from too much cycling or during resting. Do remember that too much exertion can damage your penis. Pay attention to the pain limitations your body is telling you. When I restarted, my pain limitations was around 2kg of weight. After a few weeks, my weight limit is around 3.4kg. Do realize that you must allow your penis the time to progressive adapt from 1kg toward the upper limits.
Critical points take home:
1. Short burst stretches to initiate micro tears. Never force weight load beyond what your penis is telling you. Sharp pains are the limits. Dull pains before the sharp is what you're looking for.
2. Solidify the tears with new growth using all day stretcher (ADS) or wrap with constant tension no greater than 1.2kg. I do emphasize on the 1.2kg limit. Do not exceed this. At the start, I could only handle around 6 hours before my glans got very sensitive. Now, I can push to 24 hours with ease again. Some like to use the traction device but it's too bulky. I prefer the ADS with the vacuum cylinder. Easy to put on and remove when needed. Easy to put tension according to my needs.
So far, this is only me, I easily cemented 0.7cm after 3 months of continual work. What you put in is what you get out.