I've never used the command myself, but I know how I'd investigate it.
First, I'd play to see what effect the smoothing value had, and whether more smoothing slows it down in the way that I require.
If not, then I'd look at affecting the distance parameter using the CURVEVALUE function, providing the current distance between the camera and the object and the required distance, and tweaking the speed value of that. I don't know what the angle parameter does, but it may be necessary to do something similar to that too.