Use your EQ settings to even out the individual tracks before you mixdown and tailor the EQ settings for each instrument. Getting a bad mix after mixing two instruments with a lot of mids? Try cutting the mid-range frequencies down a bit from one of the tracks rather than lowering the volume of the entire track. Think of EQ kinda like another volume control for mixing down. Still not good enough? Cut the mids from one track while increasing the mids from the other 'till you find a good balance.
For instance, if you're getting a good guitar sound but you don't like the sound when you mix in a bass guitar, you may have way too much bass after you mix 'em together. If the bass is overpowering the guitar but you don't want to increase the guitar's volume, you can lower the volume of the entire bass track and/or use EQ to scoop out some of the bass' frequencies (i.e. the ones that overlap with the guitar). Alternatively, you could boost the guitar's frequencies where they overlap with the bass. If you're using a dynamic mic to record the bass, moving the mic a little further away from the cabinet will automatically get the mic to record at a little less volume and it will also automatically record less of the low-frequencies without any EQ fiddling. The opposite of this would be putting the mic closer to the guitar amp to put more bass in it. I'm still learning, but this is what I'd try.
It sounds like you have the problem of a guitar track which overpowers everything else by the time you get the guitar tone you want. You can experiment with adjusting it's EQ to fit it in better with the other tracks or adjusting the EQ of all of the other tracks to fit the guitar. However do you it, it's probably best to start with mixing and EQing two instruments first, get them sounding good, then add one more instrument, mix and EQ, and repeat until you have all the instruments in. Hope this helps.
