Automating dry/wet amounts in send

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
 

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

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.

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.

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.
 

Thanks for all the suggestions!  Let's see if I am understanding them correctly:
 
Currently the reverb bus is being used by other tracks as well.  If I want to keep doing that, then it sounds like I will need to continue using 2 sends.  Promidi said that there could be a way to group the controls so that as I raise one send level, the other send level is automatically lowered.  This sounds like a neat trick, but I don't know how long it takes to set something like that up.  It's definitely something for me to try out when I have time.
 
For this particular song, it's a moot point, because I realized, after Craig pointed it out, that the effect on the reverb bus isn't 100% wet.  So, I can never get a "true" wet/dry range from 0% wet to 100% wet unless I create a second reverb effect which is 100% wet.
 
So, I have a couple options of where to create the second reverb effect: I can either create a new reverb bus or add the effect to the drum track's effects bin (in which case this would be called an Insert Effect, correct?).
 
If I create a second reverb bus (with a 100% wet reverb), to be used only by the drums, then I could set the drum track's output to the second reverb bus, and then automate the new reverb effect's wet/dry slider (assuming there is one).  In order for that to work, I would need to create a MIDI track for storing the reverb's automation, correct?  Or can we assign automation envelopes directly to buses too?  (I'm a bit fuzzy on effect automation). 
 
Of course, a simpler way would be to add the new reverb effect to the drum track itself.  I could then automate the effect's wet/dry amount directly within the drum track.
 
Does that sound correct?

Sanderxpander
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).

you don't need to automate the dry signal. only the wet (reverb fader)
however, now im starting to believe an Aux track might be a better idea
typical of me, changing ideas all the time. 
 
but similar to this:
https://www.youtube.com/watch?v=GzZD-Cj_X1g