Mutual masturbation. Or masturbate while making up erotic stories that you whisper in her ear as you tickle her with sex toys. Once you've hand-loaded and fired a few over her bows I'm confident that you will be up to pulling aside her, grappling her gunwale-to-gunwale, and running out the guns for a glorious broadside that makes her strike her colors
My belief is that you ought to tell her what you are trying from the start. She may find it hot that you are doing these things, i.e. jerking off and intending to spend yourself as she watches from up close.
I was worried about performance when I broke up with my wife of 25 years. I now have a wonderful lady who is cool with the fact that I don't always finish with a bang, and I was able to stand up and be counted the first time we called upon my courting tackle for service. I didn't cum the first time we joined, but then again, we went at it for 24 hours that first date, and made each other very happy