Ozone 5 even if the less I use it, the better. PSP VintageWarmer for that tape/analog warmth, same thing, sparingly mixing it in.
My mix/mastering rule #1, if it sound bad before mastering, nothing will fix that. If it sounds great before mastering, any small nudges will mastering tools will make it hopefully sound even better.
Frankly speaking the best goal is just to use adaptive limiting at the mastering end as the mix up to that point is well glued together.
PS: The most common beginner mistake with mastering is to compress the signal to death as well as squelch out the transients that makes the music sound nice to the ears.
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