I use 3 for leader, x for required number of frames, and 3 for the exposed tail which becomes the leader in the camera.

If you can figure how to tape the film to the spool in the dark, close it up, then turn on the lights, you will get a few more frames.

I have since gone to a bench winder where the film goes off the big roll to a spool in the dark. Not for the inexperienced.