You are right : the pain is ignored by the woman when she obviously ENJOYS. My lovely 3rd wife requested very hard slapping on her two small boobs, quite often SPANKED as intensively as her buttocks ! Always in standing up position, I was happy and PROUD watching two young men vigourously spanking both sides of my wife's body becoming RED, continuing with a good FRICTION with stinging NETTLES. Of course two nice women were also playing the same way with my ass and my genitals until I éjaculated in her hands !
Such great ones for slapping. You don't always want great pain; you want to just cross the line between pain and pleasure, and see if you can make her cum. Maybe more than once.