I was watching "Memoirs of a Geisha" the other day, and I was amazed while watching the daily ablutions of the geisha, that she would apply the white makeup with the sharp dart shapes, that were left open revealing her skin color, to the back of her neck. This seemed so impossible looking in a mirror that reflected into a mirror behind her and using a large (3" flat?) brush to apply it! Thats some talent.
One year at our annual Day of the Dead party I painted myself as a Corpse Bride where I continued the paint from my face down my throat and onto my chest. My chest was painted with my ribs showing, and behind my ribs was showing my heart. While I was painting myself by looking in the mirror, my mother was watching me, and all night she talked about how incredible she thought it was that I could do that in the mirror. (I don't have a picture of myself from that night... so here's a different Day of the Dead party picture of Bob and me!)
I have also hennaed myself in a mirror. My friend Lily had hennaed herself with her non-dominant hand while looking in a mirror to see her upper arm, so I used that idea as one of the monthly challenges on the Henna Page Forum. That was really a challenge!
The problem with trying to do Body Art on yourself is not in the reaching, but in the seeing.