If you are lucky enough to have had a long term threesome, there is no humiliation in cleaning up your lady. Take turns, she surely will get off just seeing and knowing what you are doing for her. Great threesomes get all your kink on and enjoy it.
I'd like to suck the cocks of my girlfriend's boyfriend's getting them fully erect then guide their hard cocks into her wet hairy pussy and rub and lick his cock and balls while they fuck until he fills her with sperm. When his cock slips from her pusy I'd suck it clean then lick his sperm from her pussy as it runs out of her