I guess the sellers won't always go with it, but you can arrange loan terms at a bank or credit union prior to shopping.

For example, even huge banks do this: https://www.bankofamerica.com/auto-loans/

Smaller places might have a car buyer that does everything for you.

Really, the trick is to get a good price on the vehicle and then convince the dealer that you don't want their dirty, obfuscated, expensive loan.