Originally Posted by andrewwynn

You do have to push the brushes in while assembling and there is very little space. The answer is practice and experience. I usually find some very thin tool like a dental pick to assist with that issue.

Do you have valeo or Bosch?

You can drill a tiny hole in the plastic in just the right place and use a thick paperclip if needed to hold the brushes back also if you get close spin the armature if you can (might be impossible with water cooled model) to help seat.