Aside from the beltings, Mary Lou gave Credence weekly maintenance spankings - the classic, over-the knee way with her bare hand, scolding him for his past and future sins, but also telling him that she loved him, that these were for his own good, etc. She kept up the practice well into his teen years, so they became Credence's only foray into sensuality, due to the ambiguous physical/emotional closeness, and finally the only way he can become aroused.

After the events of the play, Credence falls for [character of your choice], but thinks he won't get hard/keep it up unless he's told to bare his bottom and lie across their lap. Cue shame and anxiety, until his partner finds out in the end and reassures him that it's perfectly fine as long as it's consensual. They try it out, with partner being careful to turn Mary Lou's scolding into praise* and checking that it's a truly erotic experience, and getting super aroused by it too.

*I'd rather they did not go into BDSM/powerplay territory, rather the partner telling Credence how gorgeous he looks, how they love giving him pleasure, etc.