Focus not so much on actually kissing the mirror, just looking through the curve with your head SOMEWHERE between the windscreen and the mirror.
If you look at Marquez in this picture. The key takeaway is if you draw a line along the spine of the rider, it is parallel to the bike's center line, || and not \/ or /\. If your butt is off the seat, make sure your head and shoulders are following.
One more thing is that some riders sit too far forward, against the tank. This locks their hip on the seat and doesn't allow them to move off the bike properly.