The thing I find with panning is that its not really a mixing thing because if you pan something one way you have to pan something else the other way to
balance it out. So in mix terms I pan to balance left and right.
So say you pan a high frequency range instrument to the left, say a high hat or whatever, you have to have something in a similar frequency space panned in the opposite direction to make the mix sound balanced. Or not and leave it intentionally unbalanced. So the left and right spectra need to be a similar shape overall. So panning in mix terms is, to me, is about making the overall sound central and balanced left to right....stereo spread. The more frequency space a thing takes up the more you have to compensate when you pan it off centre. Brass takes up loads of frequency space, unless you EQ it. Full brass is such a thick sound that to pan it off centre you would need something just as thick to balance it on the other side...or you'd have a weird mix where you're moving lots of things right to balance the brass on the left. If you EQ it then you reduce the space it takes up in the mix and therefore reduce the mix balance displacement of panning it, but then before you think about panning you have to think about EQing... so you are back to square 1: EQ. Which, combined with Gain, is really 95% of mixing.
I think you have to think about what is important. How much of the brass' frequency content do you have to have? If a lot, then you will have to sacrifice somewhere else. You also can EQ things differently at different parts of the track so you can let the brass through completely at relatively empty parts of the track or during accents but use more EQing when you need to make room for other things. The standard approach is to chop up the stems and use different treatment on each one. Its also very easy to set up EQ that transitions smoothly too. For example in Live the EQ has a scale (IIRC) knob that you can automate to reduce/increase the effect of the EQ over time.
Also, often, the point at which two things clash is very specific. If its specific in frequency then you want EQ. Sometimes its specific in time. For example a long sound like brass might clash with something stabby now and again, so you can set up side chain compression so that the brass ducks just at those times. Or you can just manually automate it's gain. Maybe you need to think about riding the gain of the brass across the whole track? One of the drawbacks of in the box production is that we tend to forget about moment to moment gain decisions made by performers. Anyone interested in orchestration knows about this. We tend to forget about it in electronic music.