There is an easy way...
Use firefox, go to iconsquere web site, search for the username you want, click on the userIDs (following or followers) you want, then, just scroll down, down, down (you can use a macro script to do that for you) and then, using a link grabber (search for that on the firefox addons website) just get all the usernames ids links to a txt... then, just remove all the extra info (http :// , links, etc) for each link that contains the user iD using notepad "search / find / replace" tool... and you're good to go... sounds more complicated then it is.. but I'm able to get around 7,000 - 9,000 users iD's in a few minutes doing that.
Cheers!