Like back-to-back? Not sure there would be a huge benefit unless you had a lot of water/oil coming out of the compressor, it's basically just like adding two filters. The problem is you need to cool the air down to change the dew point and get the water vapor out of the air. A separator just removes water/oil droplets.
I have a large separator (3/4" in and out unregulated) at the outlet of my compressor to catch the big stuff coming out of the compressor, and then I have separator/regulators at each of my drops to catch whatever may have condensed out between the compressor and the outlet, as well as allowing different pressures at different points, they also function as my drip legs.
But it's the piping in between the two that actually does the work of cooling the air so the water can condense to be removed by the separator. For that reason most of my major air use points are farther from the compressor, and when I paint I specifically use the one farthest away. I rarely see water there because it falls out and collects in the earlier drop points.
