Painting Weights on clothing

[Rhi]

Hello

I have two characters they are rigged and have been binded to their skeletons, however I'm having trouble painting the weights on the clothing, I fix one area then another is messed up and they keep going in and out of the body.

What should I do, is ncloth an easier solution or does anyone have any tips on how to correct this. I want it to look as perfect as I can get is as its my major project.

Thanks