When you're mastering, you want to push into limiters and compressors to get it sounding together, glued, and smashed together. That's the mindset that you've got, and you think that that's what you should be doing.
The problem with that, however, is that you lose all the transients and all the sharpness in front of the track. So you don't get these sweet, punchy, dynamic sounds or keep the loudness. The way I get around that – and it's a mindset thing of how you work with compressors when you're a mastering engineer, compared to when you're recording or mixing – is by using compressors for the sound of the compressor. I don't use it for compression.
When you're mixing, you might crush a sound in a compressor in the same way as when you're doing a vocal. You might want to compress it up to get more richness out of the sound. But with mastering, all you're doing with different types of compressors is using the flavour and the tone of those compressors. If you are moving the needles, you're doing too much.
What you want to do is make sure that you've got your attacks slow. What that does is it lets the sound feed through, and then you can grab it with a little bit of release. The more release you have, the more flavour it gives to the sound. Don't have the release for too long, though. Otherwise, it doesn't release fast enough, and the next hit comes along. It's about measuring that. But a lot of the time, let the transients come through the compressor, and have more of the sound of that compressor with the release times. You may want to glue the track a little bit more. But make sure you keep the attacks open because otherwise you're just going to grab too much of the front end and you're going to lose all those snappy bites.