If your sales staff could pre-qualify everyone with 100% accuracy you would never have to switch a customer from a prime sales process to a sub prime sales process.  Even with years of experience it is unlikely that this will occur. Typically, when the dealership sales staff is unable to determine the credit worthiness of the buyer they will follow the traditional sales process.  That being said, there will be car buyers that we cannot get bought, under the current conditions, on their automobile of choice.

Our task, when this happens, is to sell the customer a different car for which they qualify.

If the customer is still at the car dealership your success rate will be much higher than if they have left the car lot and you have to contact them via phone.  Another consideration is whether or not you had a deposit with the original purchase agreement.  If so, it's likely the customer will come back in.

Which tactic is best to get the customer back in and sell them a different car?  Here, is where you may come to a fork in the road.  Aggressive car dealers may choose to get the customer back in at all costs, some even schedule a delivery time and have the customer get auto insurance for the original vehicle, then deal with switching vehicles when the customer arrives at the dealership.

Others stores disclose too much information on the phone and loose many customers.  How would you respond if I called you and said, "Bob, you were declined on the new Altima, but one of our subprime lenders is willing to take a chance and give you a SMALL loan at a 25% interest rate and more money down.  You'll need a bunch of documentation to prove everything that's on the application; can I set an appointment for you to come back in?"

Before I discuss some techniques that I have found to be successful at getting buyers back in the store, I would like to talk about the psychology of the car buyer.  Many times, just to save face, a buyer would rather go to another car lot and purchase a car within their budget, than they would return to your lot and purchase a vehicle that was not their first choice.

So when talking to the customer, make sure you use open ended fact finding and alternative choice questions, and assure the buyer that they have come to the right place.
One of the best open ended fact finding questions I've used over the phone is "How quickly do you need transportation?" This question puts the customer at ease and is a natural segway to the discussion about credit.

For applicants that I have approved, and can show other cars to, I've said "The bank approved you, but declined the vehicle" if you utilize this make sure you have a good logical reason why the bank declined the vehicle.

Another method is to explain to the customer that you are getting close on the deal but do not yet have a final approval, and that the bank requested additional documentation.  Give the customer the list of STIPs and set-up a meeting time.  As you gain more experience, you should be able to isolate a technique that fits well within your personality and the culture of you store.