Plugin I use in every session part 1 : True iron is something I've been using since quite some years now. It gently introduce the analog warmth from old hardware transformers such as UTC108x or the HS40018. Those sound quite different from other coloring emulations, such as tape emulation. The simple controls come in handy, as it allows me to quickly choose the correct algorithm with a bypass button for accurate A/B. For mixing or mastering, maby you should give this a try ?