Depends.
My credit union has a "car buying concierge service" but it's basically one guy who searches all the car classifieds, and offers good advice and a sympathetic ear to people who are uncomfortable/nervous about buying a car. I can see the value, but it's not a service I need.
But if you need financing, you still have to qualify. (Income, credit score, etc.)
The places that advertise cars regardless of how bad your credit is, usually are making more money on high-interest loans than on the cars. Explanation:
https://www.youtube.com/watch?v=4U2eDJnwz_s
I would avoid. I mean, ultimately, whatever kind of car you get, you have to pay for. So if somebody leads off with "come here - nobody else will sell you a thing, but I can get you whatever you want!" then I'm already looking to walk away.
Plus they have a bunch of really, really terrible reviews online.
https://www.consumeraffairs.com/automotive/paul-blancos-fresh-start-credit-program.html
If you're really hard up for a car, your best option is probably a police auction, but you'll need cash in hand.