Dollar rental using capital one points question

I just booked a rental with dollar using my capital one points. Called dollar to add my dollar express number to the reservation. Now it sounds like I can't go directly to the car because I booked thru capital one, but can use the dollar express line. (From what the dollar rep said on the phone) Is there a express line inside or just the regular line. If in have to stay in line then I might just cancel and go with a Alamo reservation I have.

Anyone ever experience this

 

I booked a car with Budget with my Bank of America rewards pts. I was told the same thing. I couldn't add my Fastbreak number to a reservation made through a third party. I am cringing thinking of having to stand in line for a car. But then I am saving a lot of $ by doing this.

 

Third party reservations are often an issue - hotels, cars, flights.