By many reports, bleaching seems to work really well on Ash. How much "whiter" you can get than the freshly sanded wood, as Itsabass mentioned, I don't know, but I imagine countering the tannins in any shade of wood from its natural state is going to help the "brightness" factor of the final stain and keep it looking brighter long-term.
As for grain contrast, I'm not sure what the bleach would do, but there are lots of ways to bring back contrast if needed, including various color grain fillers.
I'm contemplating making this DIY. I mean, if I have to bleach, grain fill, and sand a body, then it's pretty much ready for a stain and a can of 2K satin clear is like $20, LOL! I have 2 bodies coming...I could experiment on 1, I suppose.
I'm just not sure if dying the wood is actually going to give that bright, nearly "neon" appearance, even on white wood. PRS manages a pretty good bright green color on their "Eriza Verde" guitars, but I'm fairly certain the Warmoth and possibly the Ibanez are tinted paints, not actual stains.