Go into IAD. I'm based at CJR but I live right on the south side of IAD. Did you call both FBOs? I'm a little more partial to Landmark if I'm going to leave the plane for any period because they actually do have some tie downs there. Signature will just leave you chocked on the ramp (admittedly with chocks big enough to keep an Airbus from moving).
I was based at Dulles for years (first in a flying club and then I kept the Navion there for a while). I still go in and out a couple of times a year. It's not an issue either IFR or VFR. File a flight plan either way. If you're coming in VFR and landing Dulles, use the PCT freq on the TAC chart (or the one on your IFR plates for a nearby airport) rather than calling the one in the SFRA instructions (which is just a "I'm watching the SFRA transponder" position and serves no ATC role otherwise).
I'd certainly not COUNT on a taxi connection from either of those places...allocate TONS of extra time. Fortunately the one time I had to go from HEF to IAD via the ground, one of Dulles Aviation's mechanics was going that way anyhow and gave me a lift back to my car. I come in from the south typically (just the way it works out for me from NC or CJR) and typically get vectored around near HEF and then in or put on the BARIN arrival. Departure is almost always CAPITAL EIGHT to your first fix. You may get pushed around a bit if you arrive in one of their pushes. According to info given to my wife when planning the Hazy flyin, the best times to avoid the pushes are:
Before 0630, 0730-0900, 1300-1430, 1600-1640, 1800-1930, 2030-2130, and after 2230 LOCAL
Frankly, I usually don't pay much attention and occassionally get spun for twenty minutes or so, but it's never painful.
Where are you coming in from?