In blender, I've experienced many problems with trying to find answers to solutions. There are many good methods out there for accomplishing tasks, but many times people are unaccommodating with questions because you "don't provide enough" of your problem when you're already frustrated.
This is one of the issues that I've been dealing with the past few hours. Transferring weights is a great resource that blender provides, though it doesn't seem to be too friendly sometimes. Some of the thoughts that I have about the subject may help in finding why your solution isn't working like you think it should be.
The Method:
What you need:
An Armature
A model
A secondary mesh, like clothing
The Process:
With no weights or anything starting out, select the body first. Then, holding shift, select the armature. Press 'ctrl+p' and select 'with automatic weights'. This should give your body some weights. You can test to ensure that your body is bending right with the mesh. Make your changes if you need to, as you'll be copying those changing onto your clothing.
Next, select your secondary mesh, like a shirt, and holding shift select your armature. Press "ctrl+p" and select with empty groups. Then select your body and holding shift select your shirt. Go into weight paint mode. In the tools panel on the left side, you should see a list of options. Select "transfer weights". After you press this, check your options. If they all look go, press "transfer weights" again for good measure, or not if you're too good for it. Test your armature movements and see if it's working. If it is, awesome; if not, try some debugging.
Debugging:
First, create a test file that you can erase later once you solve your problem. I find it helps to do this so that you don't screw up your model enough that you have to go back and re-do your armature and other things because you've gone crazy with subdivisions and things. One of the reasons I do this is to apply all of my modifiers to find out if that is where the error is originating. I apply all of my modifiers, go through the process, and then check to see if it works. One time it did, another time it didn't.
Second, when you are working with your mesh, you may find that one of your meshes, like a shirt, may have worked but when you try to apply a coat, the method doesn't work as well. If you're using Blender 2.74, like I am, you may need to check that "Source: All Layers" is on in the transfer weights option. This has solved most of my problems up til now.
Hope this helps. I'll update this as I encounter more problems with this method. Let me know if you have any questions and I'll try to help you figure out a solution to your problem.
