My boyfriend doesn't have experience kissing and is really bad. How can I help him?

Everything about our relationship is amazing. We have very open communication and have talked about kissing. I specifically mentioned the difference between closed mouthed kissing, open mouthed kissing and French kissing and how I don't want to French kiss and don't think closed mouthed kissing makes for a good first kiss. So we finally kissed and it was kind of bad. He was almost missed my mouth and opened his mouth too wide and used way too much pressure, he also tried to slip his tongue in and make out with me. When we said goodnight, I tried to kiss him just once but he won't just kiss me once. We had already talked about it a few weeks before it happened and it was still not what I like. How can I teach him without bringing it up in conversation again? I really don't want to hurt him and tell him that he's a bad kisser. There is no way I will break it off with him because I like everything else about him. He hasn't been in many serious relationships and I know I have to be patient with him. Please give me some advice.