Thread: Mixing and mastering service?
If you want to learn instead of hiring out, then...
I took mix & master classes from a strong engineer (Friedemann Tischmeyer) at https://www.mastering-academy.com/ I would HIGHLY recommend this training if it is of interest and in budget. It greatly advanced my mix & master abilities.
Alternatively (and cheaper) IMO the mix videos on SonicAcademy.com are quite useful for EDM style genres. PureMix.com has great stuff for rock, pop, etc. Steven Slate's training videos and sessions (with CLA, etc.) are also very strong. So there's good stuff now available in video format.