I had a great time instructing. It was my first job after completing my training. It makes life easier if you are flying in Arizona though!
If you are going to instruct, make sure you put the same level of commitment into it as you would into any other job - your student deserves it and it may save his life to have been taught by someone who gave their best every time.
Instructing taught me alot about the aircraft and about my ability to deconstruct a manoeuvre to help teach it.
About full down autos - In the States when I was there, all autos were taught to a power recovery hover. When I came to do them to the surface I had no problem with the last 3 feet!
I would ask the question - is it really necessary to push your luck each time you do it? With small, piston types, as long as you arrive at 3 feet with very little forward airspeed and lots of rrpm you will walk away - a good day!