Yeah I they recommend pumping although no earlier than 2 months after your procedure (to avoid causing dents/voids in the filler before it's settled) and I guess start pumping at least a month prior to your procedure.
Whatever pumping method you want to use, but something like 5-8inhg for 20-30 min maybe twice a day 3-5 times a week.
I guess the idea that if your penis conditioned to being stretched to 1/2
Inch to 1
Inch more than it's normal size then it is easier to put filler in there and it can accommodate more filler than someone who doesn't pump.