Have you watched some of the Protoculture's tutorials BTW ? I find his approach and courses very "serious" and gold mine for best practices.
Now the thing is, are you trying to master 'In the Box" with Daw plugins or using some 3thrd parties plugins ?
That might be where it's less applicable to follow Protoculture's courses, many times high end plugins are involved & used. But the concept behind the tools is always good to grasp IMO.
You're right about Mastering, it's an art form on it's own somehow, but I'm a big believer in all the work that comes before with levels, gain staging, frequencies filtering and fine EQing and then levels again. Once there and then pushing things & knowledge further with notions like MS EQuing, sound placement in space, mono & stereo field adjustments... You'll get this already very nice balanced sounding mix and with that you're more than half way from a good mastered version.
That also likely depends on how people are producing I think, if you're on the creative side of things and able to draft a quick mix out of your inspiration, you may not want to be interrupted by the technical fine tuning of the track... But then, will it be easy to mix & push to a correct master level when getting back to the mix ??
When another approach is to build the mix elements by elements, taking care of how everything sounds as a all during this process and slowly crafting a "technically" good sounding mix... But then, will this piece retain the originality and good digging vibes that you could have had during a "creative " session ??
IMHO, you've got to separate those 2 ways of doing, keeping "creative" & "technical" sessions for what they are and learning a all lot out of both. If you're producing in one specific genre and trying to craft your own signature sound, one may become very efficient using the 2nd approach thanks to templates, crafted presets and go to plugins & tools but when you listen to many producers, they all admit that it takes a very long time to get there. I think that's the point really, so just keep learning, trying things and most of all enjoy doing it : don't be harsh with yourself & your work and give you the time to get there...
But well, enough talk from me...
Thanks for your comments here on the forums and for getting involved in track feedback, being able to do fine critical listening on other's work is also a good way to learn about your own production level.