For anyone attempting this, here's what I ended up doing:
1. Copy the list of scraped User IDs into Excel starting with cell A1.
2. In B1 put this formula in the first cell: ="url of twitter/account/redirect_by_id/"&A1
3. Copy that all the way down the rest of the column.
4. Now, let's make the hyperlinks usable. In C1 copy this formula: =HYPERLINK(B1). Copy that down the column as well.
6. Use WinAutomation or another macro recorder of your choosing to record a macro in which you open a URL in your browser, copy the redirected url now containing the usernames we've been looking for, paste those in D1 and repeat. Once you're finished just remove all instances of "url of twitter" using the find and replace tool and voila, a list of just usernames. Of course, use a proxy if you're going to do a ton of these. Enjoy!
Sorry, my account's too new to post direct URLs, thus the "url of twitter" lines