Very easy with Calibre.
When you right click on a titel you can choose 'edit meta title' easier individual or in bulk.
In the metatitle screen is a field for the tags. Unfortunatly you have to remember to remove all the tags you don't want by clicking on the red X on the left hand of the tag screen.
You could also double click on the tag field in the listing (it's to the right of the screen) and change / delete that way.
Make a list of the tags you want so you don't make a typo along the way
