The teaching of visual navigation is one of those things which needs a disciplined approach to flying. Regrettably, all too often FIs waste the student's effort by insisting on totally unnecessary RT communications and other distractions. On the first few navigation exercises, my preference is not to use the RT at all apart from aerodrome departure and arrival. Concentrate on the essentials of Heading and Time, backed up by pre-planned visual fix points - NOT 'map reading' per se!
We also teach the 'standard closing angle' method of track correction. Let the off-track student make his estimate of track error, work out the correction time and fly it, then turn back onto the original heading. If you've left the exact original track in the GPS, there's nothing so confidence-building for the student as pulling up the GPS CDI bar when the student the SCA correction has been completed - and showing him/her that it has worked and we're now back on track!