If they are sending you Mastering ready mixes, congratulate them on an excellent technical job and master their mix. That’s what Mastering is all about, transforming a great mix into a great master. They may know this and just want another set of ears or the confidence that having a professional recognise the quality of their work. If they are sending you a mastered track. Be confident enough to say that you think what they have supplied is technically appropriate and sounds great. And that while you’re happy to effectively re-master it, they could just as easily release the version they have given you. Recognising quality as what it is is part of being a professional.

@Anthony Story Songs or Beats with a kick, snare, bass and as few extra tracks as possible are the best to get your head around the whole foundation method. I wouldn’t be too overwhelmed, of the 66 tracks, I would assume that most are vocals or instruments and they’re all things to think about once you have the kick/snare/bass process sorted. Good luck. And have fun

@Chris van der Linden if you have done the Mixing Intensive course then there are a couple of videos, especially the Locking In The Low End one, where Caleb and Kevin go through the various strategies they use to hit the right(ish) amount of low end. First, the numbers are guidelines, so don't get too obsessed by them. Second, it's easier to mix into them than out of them, so initially either hitting -5 dBFS peak or 0 VU, where the other one is below these numbers is a fine way to begin. At this point with the Kick, your challenges will either be addressing the transient (to increase/reduce that peak) or the lower ends of EQ (to increase/reduce the bass levels of the kick). And usually because we want to build into these numbers rather than cut them, we are either building up the transient, making the kick hit harder, or adding some bass, so the kick has the required level of energy. When you add in the bass, you will inevitably have moments where both the kick and the bass are being bassy at the same time. Which will whack up your VU meter. So you will need to work to cut the bass when the kick hits. Because your ears will tell you that, even if you cut those bass frequencies entirely when the kick hits, they are still playing. This is when dynamic side chained compression or EQ is called for. Meterwise, I can't recommend the SSL Meter Pro enough. It has all the key metrics on it in one simple plugin. It's annoyingly priced, but when SSL do put it on sale, which I imagine they will at some point, I am going to spam the hell out of this community.

Just use presets