While compressing the master fader can yield some great results, DON’T OVERDO IT. A little bit of compression can go a long way. Here are a few quick tips:
Don’t compress by more than 2-4 dB.
Use a slow attack. Let all the peaks come through, leave them for your mastering engineer to deal with.
Use a fairly low ratio. I rarely use more than 2:1 on the master.
Mix everything through the compressor. Don’t just slap a compressor on the master at the end of the session. It will completely change the sound of the mix. Make sure you’re mixing and making all of your decisions while listening through the compressor. Trust me."