I believe that having flying experience of any kind helps the process along. Having flown R/C first, is very helpful to a new full scale pilot (at least it was for me). Maybe convincing the full scale pilot that he will need help is the difficult proposition. They tend to think "I know how to do this in a real airplane and after all, this is a toy"!

Once they understand this, I would guess most full scale pilots will learn quicker than someone whom has no flying experience what so ever.