I have a very similar approach to
@Cawproductions I am also now 100% "in the box"
I have all my tracks go to sub busses and then "master busses" - before they go to my actual "Master Buss"
E.g. If I have 4 individual rhythm guitar tracks and 2 lead guitar tracks my routing would be:
4 rhythm guitar tracks -> Rhtyhm Git bus -> Guitar Master Bus -> MASTER BUS
2 lead guitar tracks -> Lead Git bus -> Guitar Master Bus -> MASTER BUS
When mixing I have options to reduce increase either all rhythm or lead guitars on one fader (the "git busses") AND I can raise or lower ALL guitars using the "Guitar Master Bus"
If I want to provide some bus compression to glue all of the rhythm guitars together I simply put the ssl bus compressor on the "Rythm Guitar Master" bus and all 4 rhythm guitar instantly all take on the same tonal flavour of the compressor and the same subtle compressor "movement" to glue them together
This flexibility with routing is really useful - and once you set up a template all the routing it instantly there
I take the same approach with all instrument/vocal groups
The MASTER BUS then has my mastering chain ready to go (but when I am mixing I leave this turned off so I do not "mix in" to any mastering effects - I just concentrate on getting a good mix and do a separate mastering process. Others like to "mix in" to mastering effects so this is a personal choice
A typical master chain for me would be:
Master bus compression (The SSL bus compressor we are talking about - but VERY subtly used)
Mastering EQ
Any "exciter" effect
Multiband compression
Stereo effects (usually multiband narrowing and widening effects)
Analogue Tape Saturation (if a warm analogue sound is appropriate)
Final corrective EQ - another instance of a mastering EQ for some final shaping
Limiter - a brick wall limiter set to -0.3db to avoid any clipping - as
@Cawproductions has said the key final judgement is how much to apply - the basic balance is overall volume (i.e. Getting the track to commercial volume levels to stand up against commercial mixes) against retaining the dynamics of the tracks
For me this is definitely the "dark art" bit and is purely a judgement call based purely on the song (as is the rest of the mastering but this last step is where the whole process can be made to sound amazing or all the hard work gets ruined!)
The time taken moving the final limiter to the perfect level is a big part of the process for me