Tuning means getting the blades to mate nicely along the full length. This can be damaged by cutting too heavy of a material, which the Micra sort of invites. You can snug the pivot by carefully repeening it. Once the pivot is stable, you can bend the blades to get a good constant bite. This takes care and patience. Adjust your iTunes feed to achieve calm first. Also, I sharpen the blades to get rid of dings before attempting to tune.
To sharpen the beveled face, I use a DMT credit card stone. Use the stone just like on a on knife. This will raise a burr on flat face. To deburr, I work the flat face on credit card stone or a bench stone.
On really messed up Micras, i have to go back and forth between tuning and cleaning up the flat face. Eventually, I can get most of them to cut cleanly along the full length of the blade.