Interesting, considering what hardener does, I never thought of adding it to primer.
Hardener has always made my paint shine more, would that possibly be a negative effect!!??
The next coat might not "bond" as well to a high shine surface.
I love how hard the paint gets with hardener,
this tractor would have looked like
without it!!
That is a 4 year old paint job!! With non-automotive, equipment paint.