brush replacement

[muddler]

Can someone explain to me how to replace the brushes on a DS321 type sander?

[muddler]

It seems as though the armature needs to be in place before the brushes are installed but there is no accommodation on the housing specifically for brush removal. Is there some technique for installing the brushes first and then keeping them retracted so the armature can slip by them during installation? Any help would be appreciated.