The drywall primer referenced above is also known as heavy body primer.
If you apply this primer you eliminate the hot spots where the dry
wall compound is as well filling in minor imperfections. Under texture
it'll allow some better drying control and allow the texture to cure
correctly! After having done the entire first floor gut rehab believe
me the drywall primer is a requirement the finish paint when applied
comes uniform and I used an low lustre latex enamael and it is
beautiful. Of course I also sprayed the primer with airless and rolled
the finish. The ceilings had to be popcorn texture sprayed on to match
the rest of the house. I might also add that for 10 years I ran a
paint and wallper store the customers usually followed my advice those
that didn't well they usually ended up applying additional coats to
hide the hot spots!

HTH