Lightroom 4 Keywords

To batch keywords in Lightroom, select all you want to add keywords to, Shift click if they are contigous or control click if not (on PC) then in the enter keyboard box type in keywords seperated by commas then at the bottom of the right work space click on Sync Metadata and a box will pop up and click syncronize.
The asterisk shows all keywords in the group selected.

If you have images that are stacked go to Photo_Stacking and expand all stacking to get keywords to the ones stacked.