When doubling yarn--needle size

Okay, I have some yarn I love but it is thin and I am planning to double it…how do I decide what size needle to use…gauge really doesn’t matter…I am knitting a triangular shawl…I just want to knit it fairly quickly…any help would be appreciated.

go with US 10s, I’d say–Ingrid?

I’d try different sizes and see what looks good.