Got into an olympiad's Finals in Boston (June) as a Pakistani student. How do I get a US visa in time?

I just qualified for an Olympiad's finals in Boston, and I'm freaking out about the visa situation. The event is less than 2 months away, and I'm from Pakistan, where B1/B2 wait times are apparently 6–7 months.

I know I need to request an expedited appointment, and I have my official qualification letter. But I have no idea how likely it is to be approved, what documents to bring, or what to expect at the interview.

Has anyone from Pakistan (or a similar country with long wait times) managed to get a US visa quickly for a competition or academic event? What worked for you? Any advice at all would be massively helpful as this is a huge deal for me! TIA!