In my experience, if you want to expedite your application form with USCIS, it is better to do via your congressman. File other form as normal, then after a week you will receive the application acceptance notice. Then, call your congressman office (you can find this info from google), and inform them about your reason to expedite. Congressman office will have a liaison for USCIS who will forward your request to USCIS. Any request coming from the congressman's office has a better chance to be reviewed sooner. And believe me, you can expedite any form you want through your congressman, even i485, but you need a good reason to explain why you are expediting.

Once congressman office contacts USCIS, generally it takes about 4 days for USCIS to make a decision regarding to expedite or not to expedite your form. Once positive decision is made, everything should be completed in about 3 weeks.