Hi JWL. I am not part of the VSL team, I just mix Guy's demo's, and I'm a pro ed owner.
What can I say the truth is that the bottom line is that one has to make assertive choices, decisions in the mix process based on your ears and your best judgement, at least that is what I have found. If you make a mistake you will learn from it. That's probably the single best piece of advice I could give.
One suggestions I would make would be to not use Logic plug ins, personally I don't like the sound of them. If you have to use them - then they are best avoided, especially the adaptive limiter, the linear eq is not bad if you have to. Don't try to master things until you have done all you can in the mix, before you use eq, try to place things differently in the mix, don't be stuck with traditional orchestral layouts necessarily. If you listen to some hollywood scores, they're not conventional. You just have to do what sounds best. just to add an edit here. I must say actually the linear eq in logic is not bad at all, and quite useable. but when I say I don't like the plugs in logic, I'm probably referring more to the compression and limiting specifically - not my cup of tea, but I am referring to the overall sound as well, I find much of those plug ins tend to cheapen the sound and that is especially noticable on VSL/VI material. But that's just me and certainly they have their place.
Also just to add to that as I have a moment: Mix creatively to the piece. I think it's good to think in terms of the mix being an extension of the composition. You're not just trying to get a sound, you're trying to get a sound for that piece or scene or film or whatever. What may sound great on one style or piece won't be the most beneficial for another. Mix closed on claustrophobic music, mix open-mindedly on a more positive sounding piece. It matters a lot your conceptual ideas before you even start I think, I treat mixing like any instrument playing, like composing, or anything else, if that makes sense. Just as the composer tries to enhance an emotion or scene if we're talking about film, the mixer should enhance the composition. These are just thoughts I've had myself along the way. I hope it helps you. Start at the ground up, set up your mix, get your placements the way you want, get your levels where you want them, then think about eq and compression, if you're not sure, go natural until you feel there is an instrument or secton that needs some tweaking, don't always go for the obvious thing. In eq, sometimes you need to drop the lower end rather than push up the higher end to get a brighter sound in the mix, and you often only need very little to achieve what you want. Or perhaps offset with another section or instrument by doing the reverse, or modifying a different band of frequencies to fit/sit in with the other group. Listen and compare. If it doesn't sound better, go back and start again. If you start at the right place coneptually, just as sitting down to play a piece of music, and you consider all the points you're likely to traverse along the way, and then consider your application of your concept along with some healthy creative spontenaeity - ie be open minded as well - you can create the mixes you want. it takes time and you can't rush it. Sometimes it's just one or two volume changes right at the end of the job that for me make the final difference from no to yes, sometimes I say, that's terrible, I can't stand it and I start again from the beginning.
I hope that helps,
Miklos.