This is the stuff you should use: Cairol 7th stage creme lightner Get three packets of clairol lightening activators (or it won't work!) 30 Pure white developer AND a hair dye bottle (that you mix and measure in) IF YOU CANT DO THIS, THEN WALMART MIGHT CARRY BORN BLONDE MAXI (and that works to and comes with everything you need) http://www.clairol.com/niceneasy/born_blonde/product.jsp This stuff works on dark dyed hair! I went from Medium brown to pale yellow blonde! I left it on for 80 minutes.
I also have the goal of going an ash blonde. But what happens is after bleaching your hair, it can be damaged so use conditioning treatments and a PH balancing shampoo to get the rid of the extra bleach left in your hair. I would then use a semi-permanent dark ash blonde for example by Natural Instincts.
Because after opening the cuticle permanent hair dyes won't work (at least in my experience, only the semi-permanents do). If you don't get your hair light enough you will only need to bleach it one other time with the activators. But make sure to space the bleaching sessions out or else you'll end up with a chemically burned scalp like I got.
Please take my advice on this! Also be delligent to make sure you saturate every hair and apply the bleach on your roots last! They will lighten the quickest.
Go to Sally's Beauty store for the clairol 7th stage http://www.sallybeauty.com/Creme-Hair-Lightener/SBS-320817,default,pd.html here is the store locator: http://stores.sallybeauty.com and walmart is fine for getting the semi-perm hair dye.
Maybe you shouldn't dye it. So many people have fake blonde hair but I have seriously only seen like 2 people in my life with natural jet black hair! :(.