Being lazy/efficient, I decided to script the feedback for all the junk I bought from eBay.  The following three lines will give the best feedback for all items listed in the feedback page, then you can just hit submit.  This can be entered, e.g., in Chrome developer tools console (F12, top right tab).

jQuery(":radio[value='positive']").prop('checked',true).click();
jQuery("img[alt*='Very']").click()
jQuery("input[id*='comment']").val("Great. Thanks. ")

The comment could be changed to something more descriptive.  Then I just checked through them and hit the “Leave Feedback” button.