It very easy to be honest....here's how I do it...
At the end of my girth session (Always at the end)...I'll put some �naked people movies� on, I'll jerk it until max erection....(now you have to be standing up for this otherwise it won't be effective) place the towel right on my glans and raise it 20 times....it takes less than 20 seconds....that's one set...
Then while watching �naked people movies� I jerk it till max erection again, and place the towel (while standing of course) and raise it 20 times (I'm sure you can keep an erection for this long, it's less than 20 seconds)...that's my second set..
I do 2 more sets of this..
so total 4 sets of 20 reps....as you get better you can place the towel in water to make it heavier, or you can do sustained raises...ie. keep it in a raised position for as long as you can.