How long does Kilz need to dry before skim coating?
The best suggestion is to read the manufacturers instructions on usage. This information is often printed on the paint container label. You can also check at the manufacturers web site and look up the particular type of paint you are using.

For example: http://www.kilz.com/products/primer/kilz-complete
Click on the "PREPARATION, APPLICATION &amp; CLEAN-UP" tab near bottom.