For some reason the better your mixes are, the less difference the 2bus comp will make. Years ago, if I took off the bus comp, my mix fell apart. Now it only changes very, very little (less punchy without the comp). I do mix with the compressor on from the beginning and I check that the gain reduction is 2-4db only though.
A trick for setting the compressor:
1) Set the attack to slow, release to slowest and turn up the threshold so that you get 10-15db of gain reduction.
2) Look at the needle or gain reduction meter and change the release so that the needle or GR meter is moving somewhat in rhythm with the beat of your track.
3) Then bring the threshold back so that you get 2-4db of gain reduction.
If you A/B this against compressor-bypass and/or compressor with longer attack time, you'll mostly find it is punchier. Do this from the beginning of the mix and check your gain reduction every now and then and you should be fine.