Slank: You're a faster learner than I.
It took me quite a while to get the technique down.
About your premature ejaculation issue: Some might say that if you lasted for 30 minutes, you're already golden. I would say continue to practice. You might have a few "relapses." If you do, it's normal, so keep with it.
From my experience, you can ejaculate at the end if you want to, or you could hold it in - depending on your energy level, what you have to do over the next hour or so, your health, etc. For example, if I'm sick, I try not to ejaculate at all or I tend to get sicker. Also, if I have a lot of work to get done in the next few hours, I try to hold it in as well.
Hope this helps.