Just did Jessie's yesterday 6 months old, I think its just good practice for floppy eared dogs. I think it feels good to them, like you say they lean into it and moan like it feels really good.
I use the stuff from Petco, squirt it in and rub it in then wipe with cotton ball far as I can without hurting her. They always come out kinda dirty.
Now if they stink, its time for the Vet to have a look for mites or infection. I know I'm not telling Bill anything new
She's going in for her Spay surgery and chip implant tomorrow ....fun