My wife has just made me a messy session for my birthday. We don't talk about it much because it makes her uncomfortable but I laid out lots of plates in the bathroom and she filled them with various things. My dream is for her to make me messy but since that's a long way off/may never happen, she agrees to do ours for me and I close my eyes when I go into the bathroom so it's still like I have to rely on her and trust her. She knows how much it means to me so it's nice that she indulges me even though she won't do it herself.
My first partner was definitely into it. She told me she always felt funny when she'd see people get messy on tv when she was young and she'd gotten messy at events before we dated. It didn't awaken as fully sexual for either of us until we tried it together. Didn't take long into the relationship before we were sliming each others' faces, heads, and bodies with yogurt and pudding plus whipped cream while having sex. She'd even get messy on her own sometimes and flirt with me about it. Unfortunately we were both young and immature and things didn't work out. Looking back, it was really such a unicorn situation. She'd initiate getting messy even more than I did. She preferred receiving mess but enjoyed giving it too and just 'got it' on the same level as me. It's sad that it didn't work out and I haven't done much with it since then but I'm glad I had the experience.
Though my current partner may be receptive. She brought out some finger paint soaps while showering and smacked me in the face with a handful and let me do it back. We've had a couple impromptu minor WAM things with paint and she's made references to pieing me in the face and being pied. Not sure if it's sexual for her but I think I'm going to slowly try to introduce some small things and see it how it goes.
Think I've learned that women with goofy senses of humor are the best.
I am in a poly relationship with two longer-term partners my wife and my long-term girlfriend. My wife HATES the idea of getting messy but I introduced my gf to the WAM world and she loves it. She also has many femdom fantasies which means she really gets into it.