While/when soaking the printhead, I used a small intact artist's paint brush (no hairs falling out of it) to help loosen the globs of ink. I changed the water several times as there was a lot of ink.

Also, the first time I tried printing after soaking/cleaning the printhead (my issue was that the regular black cartridge showed it was NOT empty, but printing black documents wasn't working), I still had a blank page. Next I tried aligning the printhead but got a "failed," or similar, result. Next, I printed a "print quality report" from the printer's Tools menu and that seemed to be fine, so I tried printing the invoice I originally was having issues with, and voila, it worked!

Thanks.