Request: help take white hair to platinum

Several months ago I went to a pricey colorist in Manhattan and had my almost 100% gray hair bleached light blonde.  She used a single process and applied the pale blonde coloring using foils so she did not color the underlying white strands & the effect was attractive.  I haven't been back to have it redone as it was a very expensive process.  Now I'd like to do it myself but I'm unsure of how to do it.  I want the blonde to be as pale as possible since that would avoid having contrasting roots.

I cannot use her foil technique.  I just want to know which product(s) would help me achieve a platinum blonde look.  Do I need to use a toner (she did not)?  

I am worried that I may get weird yellow or orange tones, etc.  Anyone have any recommendations for me?  Thanks!