I like to have there as little stuff as possible. The mud lives there. ...but also "warmness", so I take most "warm" instrument I have there and let it be possibly the ony one speaking to that range. ...or one of very few.
The mud I've found exists mainly in the 200z region. It's hard for me to intentionally leave it with as little instruments as possible because that's where I tend to place all my harmonic and melodic content.
Imho the trick to this are shallow filters, but higher in frequency than you'd actually give them otherwise. It doesn't break frequency ballance of the instrument too much as steep cut at 200hz would, but it pushes the low mid-end back quite nicely. You essentially don't get rid of that mud, but push it back, so "brighter" parts can shine a bit more.
I might have made mention of this before, you're eqing and mixing of the signals comes from a balance of subtractive and additive eq. Your signal chain is incredibly important here.
there's a few things that i do to all of my channels, and that's a pre eq, filters, mix eq.
the pre eq is subtractive with a gentle slope of a low cut and maybe a slight high cut (i hate really high frequencies), then comes the filter part, low cut and high cut.
the filtering process and mix eqing comes from the same reverb unit. The low and hi cuts are typically more exaggerated (be careful of inscreasing the resonance with your bandwith on the low cut. You can adjust this by setting the Q or band with to where it doesn't bump up past 0). Then you can hunt around to see where things need to be boosted, but don't over do this because it messes things up really quickly.
Some tips on subtractive and additive eq; i read some where online that it's suggested to have a small band width when taking away, but using a wide band width when adding. I don't know the reason, but i tried it and it seems to work for me. I personally think that this is so just because of the inherit nature of taking things away and adding things. You'd hope for a small pay cut but a bigger bonus right?
MSCLS, but when he was LeDoom, said the same thing about making subtractive eq. A discussion we had outside of a club in san antonio a few years ago.
So you have to kind of control the beast when it comes to where things are in the mix. But not control it to a point where IT HAS TO BE HERE OR I CAN'T WORK WITH IT.
Understand the natural tendency of yourself, the sound, and the frequency at which things happen with any help at all. That should best help you when you're stuck on something.
A walk also helps....