If I have a bunch of shapekeys active at varying values, is there a faster way to reset every shape key's value back to 0 rather than do it one by one?
You can run this line in the Python console to reset all shape key values of the active object to 0.0:
[setattr(x, 'value', 0) for x in bpy.context.object.data.shape_keys.key_blocks]
Basically, all shape keys of an object are accessible via the
myObject.data.shape_keys.key_blocks list. From there you can manipulate all of the properties. The one-liner above is just an abbreviated way of writing the code below in the Script Editor of Blender and executing it:
import bpy for skey in bpy.context.object.data.shape_keys.key_blocks: skey.value = 0.0