This thread is the funniest I have ever read. I have a big dog (a yellow lab) and yes, the "lipstick" comes out all of the time. When you wear "red lipstick" with yellow fur, you can't miss it. He has (had) a pillow bed that he humped every night. From all of the biting that he did, he tore a huge whole in it. Now we have to buy him another pillow bed.
Yes, the females do it as well. My little Jasmine humps Tucker (the lab) when he is laying on the floor chewing his bone. She jumps right on his back and violates him and he doesn't even know it. He just chews away.
By the way, they are both 9 months and were "fixed" at 5 months.