Knowing that, the most effective way to get the lowest possible price is to spend as much time with a salesperson as possible. Test drive every model, have them dig up odd questions and get them convinced that you’re going to buy. After all, a serious buyer would never take so much time if they weren’t serious.
The sales rep will see all the other potential buyers coming into the lot getting help from his competing reps. This isn’t a big deal if she/he is convinced you’ll buy.
After spending all day, walk away. And do it at the absolute last minute. The sales rep and their boss will do everything they can to get you locked in because 1) they were already set on you buying and 2) they burned a huge amount of time helping you and missing out on other buyers. They’re too mentally invested in seeing you buy.
There’s no guarantee you’ll get something at cost or at a loss but you’ll put the power in your hands and be working with someone who’s as invested in buying as you are.
The idea that you can email your way to the lowest price is far less effective. The amount of time it takes for a car salesperson to reastart one to an email is trivial compared to burning an entire day test driving vehicles with you.