DC is usually pretty efficient. I went through the NY consulate a couple of months ago. The line outside was brutal (seriously, get there 45 mins before they open!), but the processing itself was standard. Took exactly 4 business days.
My biggest tip: just print everything. Copy of your driver's license, the "Where You Stay Form", flight itineraries, an extra copy of your passport data page, everything. The staff there are strict about the rules, and it's much better to have a piece of paper and not need it than get sent to the back of the line to find a local print shop.
