The sitting on is most likely dominance, yes. Though I wouldn't correct it. Dogs need to be allowed to communicate together with one another, and frequent reminders of where they fall in levels of status within the family is normal. In other words, the higher ranking dog occasionally giving a mild dominace display to the lower ranking dog is normal. Correcting for it is just going to confuse the dogs, and can cause relationship issues between them if they see the even higher ranking member of the family (you) disapproving of the displays and thus, in their minds, disapproving of the hierarchy they've worked out amongst themselves.
Dog butt sniffing is the equivalent of a handshake. It's a greeting ritual, not a display of dominance/submission, though generally that sort of thing will follow as when 2 dogs are together one of the first things on their priority list is to determine where they rank in relation to one another.
Thanks, Chris. The butt in the face is different than the usual butt sniffing. It is really weird. Two of my dogs do it, but not the other one. They will see a dog that they know, do their introductions, and usually while playing (after posturing) they sling their butt around where it is facing the other dog's head. Does it mean "sniff my butt" again? I thought that maybe they were trying to remind the other dog who was boss? Maybe it is just a form of play?
They can hit another dog with their butt, which can be playful, suggestive
or also a bit pushy and dominant, I believe.
I have seen mine do it to initiate play. Butt to head and run.
Bella does it to Kramer in a "you still got it big guy" kind of way (both speutered) and Ava-well, Ava gives lap dances-I am not sure what her mother taught her! (also spayed-but likes to "flirt")
Then I have seen them do it (Bruno and Mariele have to jump and swipe at the same time to reach the other dogs' faces) to be obnoxious and say I'm the boss.
I will also give a butt push to a dog who is crowding me. So will they to each other.
It could be dominance in your case but my older female does it to my 2yr old rott and I can tell you now it's not because she's dominating him. She just enjoys sitting on him and she'll even sit on my leg sometime. She's a very soft dog and I think it might just be the opposite of dominance so rather base it on their characters than a simple habit like that.