I did all my negotiating by email, text, and website chat when I purchased mine. Didn't set foot in a showroom until it was time to sign the papers. (I'd already driven my brother's GTI, so no need to waste anyone's time test-driving.) What I did was shop my offer via email to every dealer within 200 miles of me that had a Sport on the lot; once they (all) accepted it, I then brought up the possibility of trading in my old car with them. Gave them the details and what I was asking, of course no dealer would come close to the trade-in value on KBB. Most of them offered the same on my trade-in and wouldn't budge without seeing the car in person, which I wasn't keen on since they'd have the upper hand after I drove 2+ hours so they could look at it. One dealer in Cleveland offered me $1000 more than the others, provided it was in the excellent condition I claimed (which it was). I forwarded that offer to a salesperson I'm friends with at the local dealer, and she beat the Cleveland offer, so I bought my car from her. I didn't hold out for a private party sale since it was 4 days to month-end (10/17) and I knew that the supply of Sport/DSG vehicles was starting to dry up.
Long story short, I would do as much negotiation as possible by email. Give them an offer, see if they accept, and you've got records of the conversation in your inbox if they try to change things once you get there. Don't deal with any dealer who will only give you a price in person; they're stuck in the 1950s and they deserve to go out of business while the rest of the world evolves. The smart dealers have already adapted to the changing market, and salespeople are finally realizing that communication via email is easier and more efficient for them than phone calls and face-to-face conversations. The ones that haven't should have gotten out of the game years ago.