The one thing that I hate most is seeing people with badly ombred hair. Their hair ends obviously shows a clear line of where they had bleached their hair. That is not ombre... that's colour blocking... in your hair. Ok rant over.
So how did I get it to look natural? I sectioned her hair off into different parts and left the dye in for different amounts of time.
Following the above picture:
Red ---> 60 minutes
Blue ---> 40 minutes
Green ---> 20 minutes
After leaving the bleach in the red section for 20 minutes, I brought the bleach up to the blue section. 20 minutes after that I did the same with the green section. (If that made any sense whatsoever)
So hopefully that helped and have fun with your ombre hair!! :D
P.S. I used the Jerome Russel B Blonde powder bleach mixed with their cream peroxide.