I didn't mean to scare you. JTL does run a good operation and the buses are clean and comfortable. You may have a painless experience. It's just that any number of variables can cause the process to move slow.
Once you enter the transportation hall (right after going through customs), turn left and walk toward the back wall. The JTL Tours desk is along the back wall, in the corner. There are people all over the floor that will point you in the right direction.