I re-bleached my cruella streak at the front of my hair, I missed that old thing. Bleaching black hair is a real mission. Trust me, I've tried every method going and been left with hair that has broken off, frayed and gone peach (that was hot!)
For safe bleaching here are my tips:
1- Use a really good quality bleach, but avoid mixing your own quantities of bleach and peroxide unless you REALLY know your shiz. I use Jerome Russell B Blonde Lightener in med-dark from Boots. For small sections I make my own foil strips and apply the bleach. NEVER apply any heat with this product, its pretty strong!
2- Keep checking the foils every 5ish minutes and when they're golden, take them out. I'd love a white blonde streak, but I'd also rather not be bald so don't take the chance. It could just end up breaking off.
3- The pictures above are of my hair before I applied white toner, so its still yellowy. You'd get a better result I reckon by applying the toner NOW, after bleaching, when the cuticles are open. I didn't, lesson learned. What I did was apply La Riche Directions White Toner for 15 minutes the day after and it really got rid of the yellow tinge. I've heard the Manic Panic one is pretty good too!