Currently using a UAD Apollo Twin with an SSL Alpha Channel hooked up via SPDIF. Next step is getting that 500 series ADAT rack I mentioned earlier in this thread.
Yes so my workflow is basically as follows:
Dry track gets sent out from the Apollo Twin and into, for example, my SSL Alpha Channels EQ section(the Alpha Channel has a insert return so you can skip the preamp)
The output of the SSL goes back into the Apollo via ADAT(it skips the preamps) and gets recorded to a new track.
Once I have the printed track recorded I group it with the clean track to keep it nice and tidy(the clean track gets muted, but kept Incase I change my mind about the track with EQ).
You can do the same thing with any outboard. Just send the signal out and back in through the outboard gear.
Keep in mind that it takes time and patience to do this as you are recording in real-time. But it does keep your CPU nice and low!