I found small magnets incredibly fiddly to use so I made this little tool that will hold them and easily release them.

Print

It's an easy print with the provided print profile. It will pause at layer 246 (24.7 mm) so that you can take the piston (the smaller part, green in diagram) off the build plate and put a 3x2 mm magnet in it (use a drop of glue if required, I didn't need it) and then place the piston inside the other part (yellow in diagram) and resume the print so the piston and magnet become caged. When the print is finished excersice the piston a few times before it's ready for use.

I suggest to print two copies in different color and orient the magnet with different polarity on each.

How to use

Make sure the piston is at the bottom and point the tool to a magnet, it will stick to the end, then place the magnet and pull the piston up and it will release the magnet.