Is there a way to prevent the weight painting to affect front facing but covered geometry? Like you have a mouth and paint the underside but don’t want the inside of the mouth to be affected.
In Fall-Off of brush panel, there is Front Face Fall-Off subpanel, where you can define an angle value.
You can enable Paint Mask, in 3D Viewport header, to limit weight painting to selected faces.
You can enable Vertex Selection to limit weight painting to selected vertices.