When the FINAL PRICE is settled this is when you tell them you are paying cash and do not need financing.

Ok, great. You do realize that:

1. Dealerships have goals set by banks for number of finance deals, and when they make you an offer contingent on financing, the deal may no longer make sense for the dealership when the buyer unilaterally upends the terms?
2. Some of the rebates that got you to the final OTD price may be contingent on you financing the car and are not available on a cash deal?

Everyone gets rightly mad when a dealership changes the terms on the customer at the last second. This includes many industry professionals. Why is it any better when a consumer encourages other buyers to play the same kind of games?

Lastly, if you aren't comfortable, WALK OUT. You have the power here, not them.

Which leaves me rather baffled why everyone thinks they need a complicated playbook when they walk into a car dealership.