Using verbs like moan is describing the sound. Moaned loudly is using the adjective, because just using moaned, no one knows if she said it softly or loudly. Rules can be broken, IMO.
I, personally, like the characters to use their words followed by an action (though I need to do this more in my writing).
Something like: "Mmm, God that feels good." She wrapped her arms around his neck. "Do it again."
My example is generic, but gets the point across.