With the Dollar Fast Lane, there is a separate line for the counter. The next available agent will call you, and then you walk to the garage to get your keys.
PS. on our last trip we had reserved an economy car. The agent offered us upgrades to a Pacifica for $15 per day or a Lincoln town car for $9 per day. We said naah and when we got the keys we had a Lincoln town car! Most of the time I end up with red Dodge neons!