EasyWeight

Heya, thanks for the feedback. Just to be clear, the add-on doesn't do anything regarding symmetry when making weight paint strokes, but yes, you should be careful with symmetry options in Blender because they can be wonky sometimes. There are however operators to symmetrize weights, and those work to an extent even on not perfectly symmetrical meshes.

Heya, this feature now "just works", you don't have to use a custom operator or custom hotkey. Just select the mesh and enter weight paint mode. The armature should be in pose mode, even if you didn't select it, or if it was hidden. It just works. If that's not the case, you can submit a bug report!