My theory on pumping and manuals...
After pumping on and off for over 6 months and being in PE now for over 2 years I think I kinda figured out why pumping and manuals work so well together.
Lets look at girth for example. If you pump alone with nothing else, the resistance of the tissue is greater than pumping alone can overcome. If you try to raise the pressure, you get fluid and no real growth. If you pump at low pressure for two to 3 hours then you’ll see some results eventually.
When you do squeezes and jelqs you really strain and fatigue the tissue greatly. If you go hard with squuezes and jelqs for 15 minutes, you’ve worked the penis enough that when you pump after, even low pressure is effective in giving you expansion without all the time involved.
Better yet, on off days, pumping allows you to bring your dick back up to full size without overworking it like you might if you did not have a pump.
Thats why I really beleive that pumping and manuals is much better than either of them are alone. Pumping is like a catalyst that speeds up the process.