That will be a matter of opinion that seem to divide modellers. Some will tell you you must always use a primer no matter what type of paint and especially when useing PE and Resin.
Personally, i have never primed a kit and i use lots of PE and use both Enamels and Acrylics.
I am a Norfolk man and i glory in being so
On the bench: Airfix 1/72nd Harrier GR.3/Fujimi 1/72nd Ju 87D-3