Explore Edging
If you’re giving yourself penile stimulation at the same time as using the vibrating butt plug, edging might be a good technique to explore. With edging, you bring yourself to the "edge" of orgasm, and then back off stimulation to cool off for a bit, before resuming play and getting close again.
Some people use this technique to hold off orgasm for hours (or even days!) The ultimate payoff is often worth the wait.
Try Different Toys & Techniques
Another option could be to change up the toys that you’re using. It may be the vibration that’s making this stimulation too intense. Try a toy from Aneros — the unique shape of their prostate massagers provide stimulation hands-free, and the stimulation ramps up whenever your muscles contract. This could offer the extra oomph of a prostate orgasm without getting you there quite so fast.
And if your prostate is highly sensitive, there’s a chance you could experience a prostate orgams without penial stimulation at all! Grab a toy like the nJoy Pure Wand, plenty of lube, and take your time.
With prostate orgasms some folks are able to experience multiple orgasms, as you can have a prostate orgasm without ejaculation (and it’s the ejaculation that requires refractory time, not the orgasm.)
The prostate isn’t the only sensitive area when it comes to anal play. In fact, the whole anal region is full of nerve endings with the potential for pleasure. If penetration is too intense, try external anal massage as part of your play routine. With plenty of lube and trimmed fingernails (or better yet, gloves) you can provide a range of sensations to spice up masturbation or partnered play.