Question about weight painting

This issue has been bugging me for ages. I’ve been using Blender for years now but I still have yet to find anyone even discussing the issue, which is even more mysterious to me than the system itself.

How exactly does “limit selection to visible” work in relation to weight painting? I remember for an extremely long time the functionality was such that it was affected by the switch in EDIT mode. Now it seems there’s actually a button for it in weight paint mode, but even now that I understand it better I still have many huge problems with it.

I’ll try to keep it simple:

  1. Is there a way to make it so the actual back faces of the model are not used in the calculations by the blur brush?

If you activate “limit selection to visible” in weight paint mode, it becomes possible to paint even dense meshes with many obscured parts(like fur on a coat or leaves on a tree) easily, but the drawback is that currently, you’re also going to be painting anything in the radius of the 3d cursor in the view, and if you’re using the blur tool, the same holds true for its weight blurring calculations. This means if you, say, have coat over some skin on the chest of a model, if you turn off “limit selection to visible” then not only will you paint through the coat to the skin you WANT to paint but you’ll also be painting the back of the model.

I understand this is a complicated issue but I can think of several ways that it could be dealt with if there isn’t already a solution(such as limiting the effect distance of the brush in 3d space from the first face/vert it projects onto, or possibly the normals again using the normal of the first face/vert it projects onto). I would try to fix it myself but to my understanding fixing it is probably going to require C programming, which I’m still only just learning.

However, I don’t think the next issue is complicated at all, and it’s an even bigger problem in my opinion.

  1. Is there a way to make it so hidden vertices are NOT involved in the calculations done by the blur brush?

As it stands, even if you hide part of a mesh in edit mode and choose “face selection masking for painting”, the weights of invisible, inaccessible verts are used in the calculations for the faces/verts you’re actually working on. This is compounded by the issue with “limit selection to visible,” as not only are hidden vertices blended but now all vertices–regardless of whether they’re hidden or facing the view or not–in the path of the brush are used in the blurring calculation. The only way I have found to get around this is to actually separate the parts of the mesh you don’t want the brush to use but are getting in the way, which is more than cumbersome and sometimes borderline impossible depending on the complexity of what you’re trying to do.

Because of these issues in order to weight paint effectively in situations where I’m dealing with obscured vertices, I’m finding I often have to make a backup of the model, determine which areas I’ll need to paint and which are going to be in the way of the brush during this process, then split the model based on that decision, weight paint, then rejoin the split models, merge doubles, correct any mistakes that may have happened because I’ve merged doubles on two meshes with possibly different weights and I don’t understand how it chooses which weights to use between two doubles with different weights, and then create another backup of the original model and finally copy the new weights to the new backup for the finished product. This is just to paint one area where this becomes a problem and, to my knowledge, must be repeated for every area. I wish I was exaggerating. I know of other methods but none of them are even half as simple as it would be if the blur tool worked like I think it’s intended to.

Sorry if these are things that are commonly asked but I have been around for awhile(albeit I haven’t come to blendartists much until lately) and never seen any discussion on them so I’ve decided to bite the bullet and ask myself. Apologies if I come off a little full of myself, I’m trying to be to the point but it might sound irritated(although I think these are huge problems if I’m not misunderstanding).