Save the AppleScript file to /Users/{username}/Library/iTunes/Scripts
as Change iTunes Count.scpt
.
In iTunes a new menu item, the script icon, will appear. With one or more song selected, click Change iTunes Count and type in the updated play count for each song.
This still a very manual process, which could definitely be scripted to be faster. However, for fear of losing all plays; I'm using this one song at a time (it does support loopin through multiple songs though).