First I try to get a good mix with solid levels, always watching the master bus to leave some headroom, say 3 to 6 DB, and often more than that.
As a final step I apply some mastering plug-ins on the master bus. I usually just put on some master limiting to bring the levels up to something comparable to my A/B reference tracks. So the final level is very dependent on what I selected as my A/B references. That way my mix should be comparable to some kind of genre-standard mix.
I also finalize the EQ settings at this stage but if something is out of whack, I prefer to adjust EQ on the individual tracks instead of the whole mix. It may take longer this way but I believe its the best practice. If that's not effective, then maybe a frequency is building up from several tracks and I might apply a touch of EQ on the master bus.
Someday I'd like to work with Ozone or other mastering plug-ins but so far I haven't made that investment because I'm doing OK without it

Jim