I take it you are painting over a paint you previously applied?
Are you planning on stripping your last paint job?
Did you clear-coat, Enamel, Lacquer, or wax your previous paintjob?
If you didn't clearcoat/wax your last paint job you can use the wet sand able primer you have Primer sticks great to paint but not as well to clear coats. for new applications or applications where you are planning on stripping down the previous coats to bare material i like epoxy. Epoxy Primer works really well on OEM clear-coats for me, Its not cheap but it'll stick to anything. Epoxy is probably overkill if you are painting on top of a rattle-can paint job.
What color are you thinking?
13 WRX Hatch