well "mud" is normally associated with bass and bottom mids. EQing troublesome frequencies may or may not be able to help however the best thing to do is to experiment. You may also have different tracks fighting with each other and this can be tackled in two ways 1) separating them in the stereo spectrum using your pan button and 2) EQing.

so..

1) look for Mud on individual tracks. When you find it EQ that track, then have a listen to the whole mix and see if the problem has gone.

2) If not try sticking an EQ tracks you suspect may be problematic and EQ listening to the mix rather than the individual track.