Developer volumes

[StageManager]

I currently have dyed black hair, naturally dark brown.  I am planning to use color b4.

After that, I'm going to bleach my hair, I don't know how light yet.  The purpose is to lighten it, so I can dye it very blue black and get a good hue.

Since I'm going to be bleaching, I thought I would have some fun and go really blonde for a week (reccomend a good toner/blonde color?), and then maybe use some of the blue dye for blue hair another week before I go blue black.
(FYI I'm using Sally's Ion Color Brilliance perm. black, and the for the blue their "brights" line"

I have never bleached my hair before so I'm trying to understand volumes.
Should I:
A. Use a 20 volume and leave on until completely bleached? possibly a long time?
B. Use a 40 volume and bleach faster?
C. Use a 20 volume and do 2 or 3 sessions

I don't want to I plan to use the coconut oil method.


Also, what bleach would you recommend?  I was just going to use Sally's "Salon Care" brand for the developers (unless there is a better one), but haven't found a bleaching/lighter product yet.
I was looking at L'Oreal Super Blue Cream Oil Lighter (http://www.sallybeauty.com/creme-lightener/SBS-500509,default,pd.html#q=oil+lightener&start=5)
and the Clairol Blonding Kit/7th Stage (http://www.sallybeauty.com/clairol-blonding-kit/SBS-320815,default,pd.html#q=oil+lightener&start=1)

[Janineb]

In all honesty,  I'd say make no plans on a blonde until you know where you are after three rounds of colourb4. Why? Because black dyes stain and you're highly likely to ruin your hair for no reason. You don't need a blonde for blue black,  you could just put a dark blue (maybe with a bit of green to tone any red in the brown) over what you have now. That will give you a blue black.