Yes, List of tags - File - tags (or Text file - Tag is the new name) is how it can be done. It works for all the files at one time.
The steps are:
Have all files shown in the itunes library. Then click "File > Export" and choose the txt format.
The new textfile then needs to be renamed to .csv and importet in a spreadsheet program like Excel or OpenOffice.
In the spreadsheet program we go to the column with the file paths on the right and select all its entries and copy to clipboard. Then make a new normal text file in windows and paste the info.
This text file then gets renamed to *.m3u
Again in the spreadsheet program we serch the two coumns with the play count and rating info.
We make a new spreadsheet file and paste the two columns in it. This spreadsheet then gets exported to csv, with coma as text delimiter.
Now we can load the m3u-file in Mp3tag (that makes sure the files are in the same order as the play count and rating info).
Select all files, open "Convet > Text file - Tag" and browse for the csv file with play count and rating.
I suggest to use 2 temporary fields first before finally using popularimeter.
The format string could be
Finally you have all the info stored in %play count% and %rating% and can use them to fill %popularimeter% with a "Format value" action.