Yes it is very possible. You have to be kinda flexible though...but its not too hard if u stretch somewhat before hand....just apply the nair onto the backside of your right hand, bring ure arm around ure back, and apply toward ure left side of the back palmside facing out...to get to the other side apply on the backside of ure left hand to do the same for your right side...i know its confusing...but just try it step by step and I think you should see what I'm talking about....hey it works for me...
To get to the top of ure back, just apply the nair on ure palmside, reach over ure shoulder and apply it that way...
There's an online company at emen2000.com that sells a "lotion applicator" that's pretty good for this sort of thing. It's listed under the "Lord and Owen" product line in the online store.