I have seen you post this dry/wet method a couple of times can you explain in detail please?

The advantage of using a bus over a dry/wet knob is of course that you can use hi and lo pass filters to limit the compression to only the frequencies you want. You could for instance cut out the low kick frequencies. You can also do other forms of processing on the compressed signal, like adding distortion or flange (with varied results, lol).

Agree with sharke. Using a bus allows you to compress only the drums you want, or mix the compression to suit the sound you're after. With the wet/dry method your options can be limited somewhat.