if you read the comments there are certain busses you can't add plugins to, at least with this version of the plugin. Gary is working really hard to get updates to us weekly.
My mixing workflow uses submixes and parallel compression.
bass tracks go to master, and send to the 'crush bus'
guitars output to a guitar bus, and possibly send to reverb or delay
vocals to the master, send to reverb and delays
drums out to a submix, parallel compression, and reverb
right now with ATA 1.2 you can't put plugins on submixes, because the individual tracks have already been adjusted
on my submixes I usually always have some compression and sometimes eq.
Things will get easier, I don't have a lot of use for the plugin right now, but if I get a UAD card or a liquid mix then I would be using this a lot.