Weight painting in Maya....a bitch. People generally use scripts to automatically weight paint, but I'm not a MEL wizard so I opted to paint by hand.
Maya is extremely finnicky about what weight painting it accepts, and it's not uncommon to have your model explode and you just have to reload from a previous save. I scrounged the forums and theres pretty much only one way to do it.
Flood the root joint with a value of one. then lock all your joints except the root joint. Then unlock each joint and paint them by hand one by one. It helps best to start with a low opacity (like .2) then tackle higher opacities once you've painted each joint.
The smooth tool is a nightmare and I avoid it at all costs. It's best to force the program to relocating the weight values where exactly where you want by unlocking the only joint you want it to relocate to, then using the replace brush to shift the values from one joint to another. The scale brush is also ENORMOUSLY helpful in achieving a smooth transition and forcing values to shift between adjacent joints.
It's ultimately best to map out where each joint's influence is. If it has at least a value of .02 you can work on blending the transition of weights between two adjacent joints. If there is no value on a joint and it's completely black, you have to use the add brush to add a bare minimum color (the blue color) before you can work on smoothing out the transition.
I found it most helpful to paint the initial weights in the original bind pose. Then I would pose the figure slightly and analyse where I need to paint or adjust the joint influence placement. I test both IK and FK controls and pose it about 100 different ways just to preview how it will deform. I took a TON of time doing this because it pretty much dictates how the entire character looks in its poses. If craftsmanship is sloppy, people will see it clearly in the final render.
As you can see in the picture above, I didn't do the best job with smoothing out these weights in the spine, but luckily this is a cloth clothing so I can get away with a little but of unpolished weight painting.
This entire painting process, I've improved a lot from painting Monsignor so Father Tim went slightly faster. When I discovered the power of the scale brush (don't ignore this brush setting like I did) weight painting is a million times easier.
It takes a lot of time and practice to master weight painting and I believe its helpful to know in case weight painting scripts don't get the exact result you are looking for. I will definitely look into developed scripts in order to speed the process along, but I suspect that because of my extremely stylized character model, many of those scripts might have not worked as well as I might have hoped.
When programs have automatic processes its a great tool to use. It greatly speeds up the process, but to get exactly what you've envisioned, you have to go back and specify to the program exactly the results you want. ZBrush is much artist friendly than Maya is. Maya doesn't let you have as many control over more automated processes.