Who knows where the holes came from, must have been there while editing
There’s a big density difference between different mesh parts, such as A and B (viewport on the left).
The lower portion has its subdivision surface modifier applied. Very stupid, because now it has too much geometry to fix the problems, not just too much geometry where it’s not needed. It’s also the reason armature deform takes too long. Normally the armature would affect the low poly cage and subdivision would affect the result from that. Modifier order top down, armature first.
The edges had been creased wrong, or the structure wasn’t ready for creasing, which creates the angled corners and subdivision pattern on 1 and 2 (viewport on the right).
Maybe the modifier was applied to join the arm to it without subdivision. It’s not necessary to join them, especially if the thing is animated in Blender. The armature is in effect through the armature modifier on each object, and they can use the same armature.
The arm is a separate object and could then create empty groups for it. Only bones set to deform should get a vertex group, and most of them can be deleted afterwards since the arm only uses 4 bones.
- Armature in pose mode, mesh type object in weight paint mode.
- Face masking enabled, hover mouse cursor over the mesh part and press L to select linked
- Selecting the right group, could then fill the selection with the weight
– bone selection is done with ctrl+right click when the face masking is active to differentiate between mesh and bone selection
– could also assign weights in edit mode, assigning right mesh part to the correct vertex group by selecting linked mesh and assigning it from the vertex group panel or ctrl+G -> active group
And it works http://pasteall.org/pic/show.php?id=117916 separate from the rest.