I can select a range using whichever edit filter I want (lets say Clip Gain). When I move my mouse to the upper third (or so) of the clip the tool changes. So far so good. But grabbing and dragging up and down only seems to grab the envelope half of the time. Other times I have to deselect away and try again. I can't figure out what I'm doing wrong because it does work as advertised some of the time.  Any tips?

Sounds like you're doing it correctly.
 
I always maximise the track height so that it's easier to click & drag just below the top of the track to grab the envelope (or a portion thereof)

I often start by dragging the lane height out to make more room, sure there is a trade off, you lose room/real estate but its the only sure way to do pin point precision work. when the lanes or tracks are only a 1/2 inch wide its hard to do anything with accuracy and consistency.
 
Not sure if you know this:
Using the smart tool, hold down the left mouse button and drag to make a selection.
Once that area is highlighted, you can position the mouse (until it turns in to a double sided arrow) and drag up or down to move that whole section.
 
This works better than using individual nodes and working one at a time.
But to answer your question, try expanding the lane as Jonesy said.
Ive been trying to figure out a way (for years now) to set the default of the automation lane height.
Because every time I go to set 25 lanes for automation, each one has to be individually dragged to height.
This is a huge pain in the keester.

chuckebaby
Once that area is highlighted, you can position the mouse (until it turns in to a double sided arrow) and drag up or down to move that whole section.

 
This is what I've been doing, but at least half the time the tool won't "grab" the segment. I wiggle up an down and nothing, so I have to repeat the process a few times. I wonder if it's a bug, it seems to happen more on certain projects than others.

I'm not sure it is a bug wicked, if it were I think a lot more people would be affected.
 
It's possibly a mouse problem - have you got a spare you could swap to, just to rule it out (or in)?

This is exactly what I was thinking as well (what Jonesey mentioned).
Ive had issues with Logitech mice in the past, swap mice like BJ suggested and give it a shot.
Have you tried widening the lane ?

Hrm, good idea. I suppose it couldn't hurt to put new batteries in my little mouse as well.
 

Have you tried simply making sure the automation envelop is selected in the track filter, highlighting the ruler for the desired time, then clicking the selection button for the track?
 
The only warning is you need to ensure that no other track is selected at the same time...
 
Dan

Not to that effect, but this happens when I'm working on a track with the envelope highlighted for editing. It's not absolute, I can swipe and grab an envelope section and it works as advertised, but the very next swipe won't. Sometimes it's fine, sometimes it's not. I thought maybe the hotspot was alien to me, but the smart tool changes to the double headed arrow as advertised.
 

Wicked,
Sometimes changing the Tracks / Lanes filter back to Track/wave , then back to the Automation fixes the issue for a while.
I know what your saying. this hasn't happened to me in a while but it used to rear its ugly head while doing Gain automation only.