This is somewhat personal preference, but ONLY experienced guys should consider doing any more than ~5 minutes of jelqing before or after their Bathmate session.
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If you have not had (and consistently used) the Bathmate for 3 months or more, do not even consider this.
The first month of Bathmate is mostly about getting used to it.
In months 2 and 3, your penis is still getting used to the pressure, so you should only do jelqing before/after your Bathmate session after 3 months of consistent use.
If you have been using the Bathmate for 3 or more months consistently, you can jelq before and/or after using the Bathmate.
The most advisable thing to do here to get much better results is to jelq before entering the Bathmate.
It is important that you slowly get used to jelqing before using the Bathmate and start by doing short sessions (3-5 minutes of jelqing, then 3-5 minutes of Bathmate) and slowly work your way up, just as with the Bathmate alone.
There should never be any pain to this at any point.
If you are experienced (at least 3+ months of regular use), jelqing prior to using your Bathmate will create further expansion and a significant amount of pressure.
Newbies shouldn't consider this however.
Overall, it's mainly a matter of personal preference but most will find that their penis is too fatigued (or expanded) to perform jelqing exercises following a 10+ minute Bathmate session.
For more information on all the models of the Bathmate Hydropump, check out Good Looking Loser's Review and FAQ.