This is alot like asking “how hard do I push a door to open it?”
Hard enough to open it!
You must start somewhere, so I suggest use a moderate amount of vacuum that still is “pleasant”.
If it is unpleasant or painful…way too much.
So, when you reach a pleasant fullness, stop adding vacuum and wait until you feel you are maximally hard in the tube.
You can do this my feeling the base of your penis that ISN’T in the tube…if its hard, you are fully erect.
Now, take a permanent marker and mark where your penis goes the furthest in the tube. (Mark the tube)
This is now your baseline.
Start with a beginners routine for time and sets.
When you are done, do you have any signs of over doing the vacuum?
This is red spots or bruising…later on are your erections better or worse?
If you are getting any skin bruising or spots and your erections are worse…you are using too much vacuum.
Using your base line mark, you now know that if your unit goes up to that mark, your vacuum is too high… so use less vacuum.
Once you get your baseline,then you can begin to go by how it feels.
You will get a feel for what is good and what is too much.
In the beginning it is much better to err on the side of too little.
Just remember, it should ALWAYS be a pleasant experience! If it isn’t…you are too high in your forces.
But really, a mity vac is $30.00 at AutoZone…crazy not to buy one. Good pumping is a precise exercise, with the difference between growth and no- growth as little as 2 in hg!
Its the only penis you have ( unless you’re gay :) ) so spend a little money and do this right.