I've become converted to using the skinny chalk sticks in the mechanical holder (
http://www.amazon.com/Dritz-Quilting.../dp/B001UAJ7C6), but I
have had a couple of cases where the chalk has not entirely washed out. I tend to be pretty heavy on the chalk - a more sparing approach would no doubt be better. I also tend to mark as I go, so I cannot comment on how well these would last if you did the whole top at once, but they do last well if you mark half a dozen blocks at a time.
I have not tried them for handquilting yet.
Alison