I have never tried with a Bal bag. But when my leather wallet got ink stain, I used Mr. Clean sponge. I have read about it on Gucci forum. The stain was gone nicely. The wallet is Prada saffino leather one. I think it is easy to deal with kind of leather, not so delicate, though.
http://forum.purseblog.com/gucci/i-may-crazy-but-mr-clean-magic-eraser-641902.html
Good luck!
http://forum.purseblog.com/gucci/i-may-crazy-but-mr-clean-magic-eraser-641902.html
Good luck!