you can chain up the mast and lay on the floor, and get a 1/2 of them. and get the others from inside under the floor pan.
BUT...
it is my experience with these trucks and their controllers, that, overall, you will be much happier in the long run if you pull the motors (about the same time frame as changing the brushes with out pulling the motors anyway,) and have someone that specializes in forklift drive motors to 'go through them'. These controllers are famous [in my little forklift-filled world] for being 'sensitive' to brush-commutator conditions, and for the motor housing picking up debris from the floor through the air vents in the brush covers, that may cause the problems that required brush replacement in the 1st place..
as far as where to get the brushes, I strongly recommend using the OEM brushes and paying the $, also because of how sensitive these controllers are to less than perfect brush commutator interaction.