My Boyfriend is NOT Good at Oral Sex

Dear Dr. Betty,
I have a very loving and attentive boyfriend who has just one unfortunate flaw...oral sex. He gives it the old college try but, he is not very good at it. While I applaud his effort unfortunately my clit is not pleased. I have tried my best to guide him but, it does not work. He feels terrible about it and I try my best to console him.
Is there anything that I can refer him to help him adopt a better technique?
Dear M,