I've got a reverb bus, and want to vary the wet/dry amount for my drums, using any values between 0% and 100% wet.  Ideally, I would be using one automation envelope rather than two.
 
Currently, I've got the following setup:
 
1) master bus - no effects, the final bus
2) reverb bus - has reverb effect, and outputs to master bus
3) drum audio track - no output, but instead has one send to reverb bus, and another send to master bus
 
This lets me vary the drums' reverb amount, but I have to fiddle with 2 envelopes, since when I increase the output to the reverb bus ("wet"), I need to decrease the output to the master bus ("dry").  A bit of a pain.
 
Also, whenever I load my project I get a warning about the drums not having an output. 
 
Is there an easier way to do this?
 
Thanks
 

Have you considered grouping the two controls together and then using group manager to invert the range of one of the controls....  Configured this way, increasing the output to the reverb bus will reduce the reverbs send level...

Did you set the reverb to wet sound only, so adding more dry to the reverb doesn't add more dry to the output?

If you don't NEED the reverb for other sounds you could just use it as an insert effect on the drum track/bus and automate the plugin wet/dry control.

I would set it up the same way you set up a parallel compression bus.
this way you can use the fader to control the reverb signal.

Change this:
 
3) drum audio track - no output, but instead has one send to reverb bus, and another send to master bus
 
to
 
3) drum audio track - output to master, one send to reverb bus
 
Dan

dcumpian
Change this:
 
3) drum audio track - no output, but instead has one send to reverb bus, and another send to master bus
 
to
 
3) drum audio track - output to master, one send to reverb bus
 
Dan

Yep, that's what I'd do.

There's no real benefit to that for the described issue. In fact, unless you ALSO switch the verb send pre fader, that setup won't even allow you to have an "only reverb" signal.

as I said when you create a parallel compression bus, your mixing the dry and wet(compressed) signal together and using a fader to control the amount of compression. instead of using compression the bus, inset a reverb instead.
this typically what I do. there's a few ways of dong this . good reply's I've read above as well.
 

That would still require automating two faders which is what the OP asked to avoid. I think the only way is to insert a reverb directly on the track/bus and automate the plugin's own wet/dry balance (or create an fx chain macro knob if the plug has two separate controls for wet and dry level).