Personal approach :
Set RATIO to max
Set THReShold by hear, it lowers volume.
Increase GAIN
Adjust all parameters to taste :
ATK increase : more transients level
REL decrease : more pumping effect
Decrease RATIO for a more natural effect.
Extreme settings :
ATK 0
REL 127
THRS 0
RAT 127
GAIN 20 or more
MIX 127
RMS is quite subtle, increase it theoretically for a master mix.
RMS adjusts the way the compressor works. A zero setting makes the compressor look for amplitude peaks and a max setting makes it react to the overall energy level of the signal.