Hi cliff,
I suspect there will be multiple ways to do what you are looking for, so you may need to be a little more specific. Do you have a text file with keywords already? Do you know what keywords go with what filenames in advance? What are you starting with right now?
For example if you had a text file like this (Or a spreadsheet)
DSC_1234.jpg keyword1, keyword2
DSC_1235.jpg keyword1, keyword3, keyword4
DSC_1235.jpg keyword4, keyword5
Then yes you could use Photo Mechanic to apply those keywords to your images quickly.
If you have a textfile with just keywords, like this
keyword1
keyword2
keyword3
keyword4
keyword5
Then you can load those into Photo Mechanic to then be applied via the keyword panel.
Is this what you are going for? Let me know and I can be more specific
-Mick