Negotiating Tips?

Decided what BS I want; flexible on few items and colors. Also willing to walk away from Ford altogether if salesperson wastes too much time. Found a few at dealers not terribly far away, and figured out what incentives would apply, which seems to be pretty clear from websites. (Nearest ones don’t have what I’m looking for in stock.) None deviate from internet price over phone, saying that requires coming in so they can discuss with manager. Going to get finance quote from credit union and maybe get ford credit prequalified. Anything else I should do before visiting the dealers? Also curious to learn what %age off MSRP folks are getting on new BS’s (‘24’s are presumably best deals rn but I appreciate any potentially relevant info).