primers

Primers and primer-surfacers actually "Flash" quickly.  This means they dry to the touch faster than paints, but they still need time to cure, about 2 hours for primer-surfacers, half that for primers.  Both flash in just a couple of minutes in normal heat/humidity conditions... With airflow and mild, dry heat, you can speed it up even quicker and be ready to paint in 15-20 minutes.. 

Among other things, the drying/cure time of any paint will be dependent upon the paint itself, the thinner used, the application thickness, the ambient temperature, and the ambient humidity.  There may be other variables as well.  Bottom line is that you have to see what works for what you are doing.