I would like to lift all my hair by making it subtly lighter, like one or two shades max. No highlights, just an overall lightening, I am currently medium to dark brown. At the same time, I would like to cover 10-15% grey in the process. Most of the grey cover products I've seen, seem to focus on keeping your natural color and just targeting the grey but can I use this product and also change the shade of my color slightly? Any help?