Using "Kilz" primer in 3 coats with sanding in between will fill spirals far better than regular lacquer primer.
It must be topcoated/finished with enamels and NOT lacquer or Dope.

I too find filling/sanding tube spirals a tedious and borderline WORTHLESS nuisance for something that is supposed to be a fun hobby.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !