It seems like lately alot of word is gettin around of how to Sidechain in Waves C1.
There's another method VERY similiar to the one you mentioned.
This way is from The Trance Exeperience DVD trance producer Torsten Fassbender and it was also very similiar to a sidechainin artlicle i found at this link...
http://audiostation.blogspot.com/

Here's the one from Torsten....

1.Create a Track with a Kick

2.Create a Duplicate of that Kick on another Track ( Named Signal, Trigger or similar ) and pan it to left channel.

3.Create a Track with Bass ( Pad , or what ever you want to be ducked ) and pan it to the right channel.

4.Create a Group Channel Track ( i name it sidechain Group 1 )

5. Route the output of the copied Kick Track ( signal ) to the Groups Track.

6. Route the output of the Bass ( sound to be ducked ) to the Groups Track.

5.From the mixer goto the Group Track and right click on the Group Tracks panning section, choose "Stereo Dual Panner", and move the right channel to the center. ( Torsten says to move the left channel to the center also but in his project files from Trance Experience he has the left channel still to the left i guess it doesnt matter, take a listen. )


6.insert a Waves C1 SC in the Inserts channnel of that Group Track.
You'll see the signals ( kick in this case ) thumping in the blue gauge.

7.Set the Waves C1 SC Key to "L>R" ( L provides the the sidechain signal and R is the signal to be processed ), and adjust the attack to 0.01ms, Release in between 30-100ms ( depends on source material ), Ratio 2:00:1 ( as a starting point ), adjust the makeup gain to about 6DB, finally adjustThreshold to your liking for the effect.

Torsten says the reason he crreates a copy of a track for the signal is because when ever the main kick goes out in the track the ducking wont be triggered, even if you want it to be.
So with havin a 2nd copy/signal in benifits to keep that effect going while the main kick dropsout during your song.