The flow at IAD is relatively easy. Post CBP, simply take your bag up the closest escalator and the DL counter will be to your left as you face the roadway. There is also an elevator if you have your bag on a cart. Should take an extra 3-4 minutes to get to the DL line. You will then check the bag at DL, head out though a checkpoint and to the gate.
No reason to head to DCA unless you find better timings which make it worth the hassle of a drive.
Last edited by Often1; May 10, 2019 at 9:18 am