Seeking advise on sidechaining vocals in final mix.

I never do this. I don't push the levels that hard.
 
When I mix there is usually plenty of head room for the vocals without turning everything down when they come up.

bitflipper
You can even manually draw automation for an ordinary equalizer. Just use a spectrum analyzer to identify the main frequency bands for the vocal to decide how to automate the EQ. It's not easy or simple and takes some trial and error, but you can make it work.

This I do.

Great thread...what would you recommend for the kick, which fights with the bass, even though I try negative eq techniques so that they don't fight for the same space?
 
In Sonar, ducking would not be easy, as I have not seen anything in X3 that even reminds me of ducking.
 
In Ozone 5 I have side chaining capabilities.

For a more cost-effective solution, have a look at side-chainable multi-band compressors and dynamic equalizers. These types of plugins can help justify their cost by doing more than just sidechaining.
 
The least-expensive side-chainable equalizer that I know of is Meldaproduction's MDynamicEQ, $94 but was recently on sale for half price and might be again. With it, you can configure up to five filters to carve out just what the vocal needs and then modulate them as a group via the key input. Works for kick/bass mitigation, too.

TremoJem
Great thread...what would you recommend for the kick, which fights with the bass

If a little eqing of kick or bass can't solve the problem I'd try side-chain compressing the bass so it briefly ducks whenever the kick hits.

Insert a compressor with side-chain capability on the bass track or bus if there is one. I generally use one if the pro-channel compressors for this. This compressor is additional to any you might need for general level control of the bass and is probably best placed after the eq.

Set up a pre-fader send on the kick drum track with output going to the compressor's side chain input. Now the compressor will cut in every time the kick sounds.

Set the compressor to suit so that the bass no longer tramples over the kick's transient. I'd start with a medium attack then try and make the compressor as unobtrusive as possible. The idea is to let the initial impact of the kick be felt. You don't need a multiband compressor for this job. The send level on the kick track will also affect how the compressor operates so it can take some trial and error to get it working properly.

If you don't have a track dedicated to just the kick but, say, all drums on the same track, then so long as the kick's timing is good load up Session Drummer or whatever drum programme you use. Then sequence a kick line that matches the one on the drums. Set the VST kick track up with a pre-fader send to the comp. sidechain. Pull down the fader on the VST kick's audio track and you will now have a new kick track that works the sidechain while not appearing in the audio mix.

Another option if the drums haven't been split to different tracks is to duplicate the drum track. Then use eq to remove everything but the kick frequency. It doesn't matter what the result sounds like because you can use the new track just like the VST/MIDI one. Ore-fader send to sidechain, turn the track volume down so it's not audible in the mix.

It's also worth checking nothing is smearing the higher frequencies of the kick. Kick drum transients can contain some surprisingly high frequencies from the beater strike.