Did you use salt?
The problem you are having is called chalking and salt is one of the ingredients said to help with the chalking.
The basic Whitewash Paint is,
12 cups hydrated lime
4 cups salt
2 gallon water
Chris
On new exterior builds I put on 2 coats Alkyd-based Primer and one to two coats of a Acrylic latex paint. As for a brand name I like Benjamin Moore.
Alkyd-based primer Dry Time @ 77°F
– To Touch 4 – 6 Hour
– To Recoat Overnight
Chris