Alternator Brushes

 Hi all,
 the last time my son's SW20 was on the road was when it was brought up from Vic by the vendor.
On the trip he had the (not) charging light come on and was using the old tap the alternator with a hammer method to get it charging again.
Most likely cause is the brushes not contacting the armature correctly, perhaps because of dirt/dust, but undoubtedly the brushes are worn down as well.  Do you know if the brushes easy to replace ? Any tricks? Special tools ?