I personally feel that it is more intimate to rub my face against my K9 lovers faces and to let them do the same to me. I know that it's their way of marking me as their territory and I am fine with that.
I do this often in front of my friends and family, to them its just a guy being affectionate with his pet. To me it's a bit exciting to know that this is our way of being intimate and romantic, so when my female friends are saying "Awwww" or my family is saying "That's just adorable!" I know that my K9 husband and I are just being Lovers. But when I was younger and I was just learning to accept my sexuality with animals, I would feel a bit of naughty excitement when a friend or family member would walk in on me and my K9 wife, rubbing our faces together. The first time that happened, I was in my early twenties and one of my friends spent the night at my house and walked in on me with my K9 wife. We just got done making Love and were laying in bed, I was naked and we were cuddling and rubbing our faces together. He was shocked that I was naked, but understood that I had talked about living in the nude prior to him seeing us that way. He laughed at the weirdness and he never made a fuss about it.
I think some pet owners know that Dogs usually "Kiss" humans because the person ate something delicious and dogs will lick inside your mouth to taste what you ate, but there is also the possibility that it's a way to bond with humans.
I used to do this with the strays that I fostered when I was younger, I volunteered at the "Animal Shelter" and on Weekends, Holidays and other special occasions. I would foster strays that got picked up and having "Make-out" sessions was something, younger-hornier Me would do with them.
So if by chance, you find yourself in my neck of the woods and you are taking a walk in one of the woodsy parks in my town. You happen to see a Native American guy sitting or laying under a tree with his dog and they are rubbing faces with each other...Just know it might be me and my K9 husband "Making Out" during a little picnic.