render order/ multipass shaders (hidden surface shader path)

Is it possible to render one material / shader with two passes in different Queues?

I have a character surface shader and a pass for rendering the character with special color behind objects (zfail). It is important that for multipart characters all special passes of all character (parts) are rendered first and then all surface shader passes of all character (parts).

I gave the pass a different Queue Tag but this changed nothing:

Shader
{
  Subshader
  {
    Pass
    {
      // hidden surface pass
      Tags { "Queue"="Transparent-2" }
      // ..
    }

    // main rendering surface shader
    Tags { "Queue"="Transparent-1" }
    // ..
  }
}

Am I doing something wrong? Is it possibly what I want or do I need to solve that with custom scripting (and painting)?

Queue is not a Pass tag. It is a SubShader tag, and has no effect within Pass{}. You’ll have to use multiple materials to do this, if you really have to do what you said you need to do. Try to think of a way to avoid that if you can, as Unity doesn’t make this easy on you. It’s not a big deal if you only have one submesh, but if you have multiple, you’re probably out of luck for that object.