Balsa Fillercoat and Sanding Sealer "toughen" the balsa; the fillercoat fills and penetrates making the balsa "denser" which prevents easy denting, and the Sanding Sealer gives a tough "plastic like" top coat further toughening the balsa.
Primers do virtually nothing to toughen balsa.
For Basswood or ply, primer is actually plenty.
Not so for balsa unless you want easy dentability.

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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, and HAVOC !