Can you leave the metal shields on and effectively flush them or do you need to remove them?  How do you remove them?  I was all set to flush the spool bearings and I couldn't for the life of me get them off.

You don't have to remove them. The shields are held on by a small c clip. You can use the point of a thin wire hook to remove the clip and shield if you really want them off. There's no need though just to flush them out.

I don't know about other reels but if you have a Shimano, it might have bearings that don't have removable shields. A guy like me with bad eyes might spend an hour or more trying trying to find a clip that isn't there if you don't know that. LOL

Ya, some are removable and others aren't. Open bearings are easier to service but shielded are serviceable. Soak and flush 5-10 minutes at a time in the preferred solvent repeating as necessary until solvent remains clear with no signs of contamination. Dry thoroughly, spin test, oil, reinstall.