I like to gently compress my drum bus, and gently compress my bass, if needed and if it adds punchiness to the sound (as desired to taste). On the master, I gently compress again, no more than 5db GR and only on the high peaks (snare, kick, usually snare), tiny bit (2db) makeup gain if needed. Then, soft-knee limiter, only a couple of db (2-4ish) GR and again *only* on the wild peaks, unless I'm looking for that smashed effect (typically NOT haha!). "Eyeblink" is a good descriptor for what I like to see happening in my master compressor and limiter.
-6db RMS holy shit dude. *covers ears* I was taught -12 is a good number but I usually end up in the -11 to -10 range, -9 tops and certainly not for the entire track!