A properly set winder will not damage your automatic. What you need to realize is that the watch only needs a few hundred turns a day (somewhere around 600-700 for most movements in order to maintain the wind. Many cheap winders work continuously, or have programs that keep the watch winding much more than needed, which can cause excessive wear on the rotor and winding mechanisms.
What you need to figure out is the minimum amount of winding needed. At this level your watch will not be damaged any more than wearing it daily. For me, I have a cheap, continuous winder that I have linked to a digital timer. It runs 3 minutes/hour for 14 hours a day. This is enought to keep my Omega GMT wound when I don't wear it. The total cost for this was under $70.
However, with that said, I don't really think your friend needs a winder. In your friend's situation, just let the watch sit until he needs it, then set it and wear it. This will actually reduce the wear on the old watch and mean it won't have to be serviced as much. Think about it... if he keeps it on a winder non-stop, it will need regular servicing just like if it were worn daily.