Step 16: Faired!
It looks like cancer, but it feels amazing. It's also the proper foil shape.
Next comes paint. In a body shop they'd use three different primers.
Sealer primer: to cap the pinholes in the bondo and keep it from drinking paint.
Filler primer: a high build primer for more smoothing, sanding between coats.
Some other primer: I don't know, these dudes worship Buddha and he gets mad if it's not perfect.