Perhaps you are using the wrong product ???

http://www.zinsser.com/product_detail.asp?ProductID=72

The folks that make it say it's 100% "wax free"


Hax Planks wrote:

I've been trying to dewax a quart can of this stuff for a couple weeks
now. It looks like the best I will be able to do is to get 50% dewaxed
product from it, and that is being generous. The Flexner book says to
expect 5% wax. They must be decanting the dewaxed portion off to make
Seal Coat and spray bombs and selling what's left to suckers (like me)
as regular shellac. What a gyp.