First and foremost get the thought of your own satisfaction out of your head. There are many who would disagree with me saying that the happiness of both of you is important. They are correct. However your happiness is not your concern, it is hers. If you want it to be special for her then her happiness must be absolutely paramount in your mind.
Take your time. I cannot stress this enough. Take your time. Set aside the entire evening. Better, devote the entire day to being as romantic and as charming as you can be, prior to the evening you have planned. Bring her flowers, go for a long walk hand in hand, treat her to supper in a romantic restaurant. Never take your eyes off her, and never stop telling her that she is the most desirable woman in the world, and other similar encouragement's.
That evening make sure that you won't be disturbed. Unplug the phone. Put on quiet romantic music, not rock and roll. Light some candles. Skip the wine, it looks good in movies but alcohol will reduce the pleasure of the moment. Then above all, remember what I said previously, take your time. There is no hurry, and hurrying it up will spoil things.
Sit close beside her on the couch and hold her hand. Look into her eyes and stroke her hair. Let her come to you. Do not rush her. Kiss her gently, caress her with your lips and the tip of your tongue, softly, slowly, at length. (Make sure you've brushed your teeth.) Hold her. Make her feel secure. Confess your love for her. Tell her how you would do anything for her. She will respond to you. Clothes should come off slowly and only when she initiates it.
In all likelihood you will have an erection straining to burst. Leave it alone. Deny yourself the release. If she insists on doing something about it, OK, but that is for her to decide. Whatever happens, the evening is not over until the wee hours of the morning. If she does something to cause you to come, be it oral or otherwise, enjoy the moment then get back to work. Your job is not over until she has had at least three orgasms, and if you are an artist, she could have dozens.
(Quantity of orgasms is hardly the only criteria for good sex but it works for a benchmark.)
As a side benefit if you do come, it will make controlling your second erection much easier. The ability to maintain an erection however is of secondary importance to your ability to give good oral sex. More on that soon.
Do not rush into genital stimulation. Spend at least an hour slowly building her excitement. Kiss and caress her. Explore her with your eyes and hands gently. Massage her softly with your lips and teeth in all those places that you would normally find ticklish. Run your fingers lightly over her body. Let her feel your body next to hers. Let her get comfortable with it.
The heat of the passion you share will rise. Wait and be patient. You will know when she is ready, she will be begging for it. Kneel down between her legs and run your tongue along her inner thighs. Nibble gently with the focus becoming ever closer to her sex. Her desire will reach a feverish pitch. With the tip of your tongue, lightly flick the tip of her clit and enjoy her reaction. If you've done everything real well this might be her first orgasm. Continue with your lips and tongue to gently, softly, and slowly stimulate her clit. Pay attention to the lips of her vagina and her surrounding pubis. Let your hands and fingers for the most part do this while your mouth concentrates on her clit. Be gentle. You are not in a hurry. (If your fingernails are clean and well trimmed you may insert one or more fingers into her vagina. If you do, use your fingers to softly push her clit toward you from inside her.)
She may need you to stop for a bit between each orgasm so watch her body language. Don't wait till she forces you to stop. You will know by the way her legs and hands attempt to control the degree of stimulation you are giving her. Do not let her push you away completely. Stay close and when you feel her relaxing a bit, let your tongue dart out to stroke her clit again. Watch her reaction. It is these moments that make life worth living.
If you have gone slowly and given her prolonged soft and gentle stimulation, she will perceive her orgasm as a gentle wave. Watch her body language and any other cues she may give you. Vary the amount of stimulation in sync with her orgasm. As her orgasm builds, increase her stimulation gradually. The only time to be 'rough' is at that moment where the wave of her orgasm reaches its peak.
Visualize her orgasm as this wave. As it peaks it crests, and crashes violently. Let your tongue be like the beach that the surf of her orgasm washes against. At that moment you must be present for her wave to wash upon, but like the beach, you should be firm and stable.
A woman's pleasure is like the ocean and has many waves. As soon as one has crested another starts to build. As always keep the degree of stimulation in sync with her waves. If you do this well her each wave will be higher than the last. There is no limit to how high she can go.
If you do this well, there may come a moment where she perceives the depth of the ocean from which her orgasm arises. At this moment she is having a mystical experience, and you have joined the ranks of Wizards.
Alternate oral stimulation with intercourse. Try not to let yourself come. If you feel yourself getting too close to orgasm, stop, relax, and go back to oral sex. At some point she will likely insist that you come. It is OK, as long as she insists. She is probably exhausted at that point, good job. What ever you do, do not fall asleep after your orgasm. Rather hold her and whisper sweet things to her. Tell her how happy she makes you and how much you enjoy making her happy. Tell her how much you love her.
If you do all this she will never forget you. She will be back for more, often.