Eastern PA (KABE) to Manassas VA (KHEF)

Hey all -

Planning on going down to Manassas on Saturday for a tour of the new
Potomac TRACON. Has anyone flown from Eastern PA/Northern NJ/NY area
down to KHEF?

I'm trying to determine what to expect as far as an IFR clearance. I'm
trying to do some planning so I can figure out how long its going to
take, and I hear flying around the Dulles/Regan International area is a
bit tricky. Who knows what route I'll get. At this point, I have no
idea - so I may as well file direct?

Thanks for the input!
Charlie