Laura Mercier's loose powder is truly a translucent powder. Not all "translucent" powders really are, so it's good to test it before you buy.
Also, I find that if a truly translucent powder does ever go on "ashy", it means you've applied too much.
I also like the blot powder (pressed) to keep in my bag for day.
Oh, and you may also want to look into Select Loose in NC45. It's translucent, but has a slight hint of color to balance out the two tones you're working with. Good luck