Here's what I did. I smashed the hook part of the spring (the part that rests on top of the brush) down so I could spin it around the holder. I then tied a wire around the hook part, mounted the spring on the holder, fed the wires around and through then pulled them until it spun the spring 180 degrees. Then I reached in and , with the tip of my finger reopened the hook part. Now 2 more to go. What a PIA.

Those are tough. I have a small 90° screwdriver with a flathead bit. You have to spin the coil half a turn, then slide it off of the bit onto the holder