I fixed a '74 Duster grille (usual cracked mounting legs) using this method, as well. Worked like a charm.

Just make sure you let the repairs dry long enough before sanding. The tip didn't say anything about the ratio of acetone vs shavings and I think my "putty" was a little too wet when I applied it. After letting it dry overnight, I found that it wasn't real solid below the surface when I started sanding.

For good measure, I let the repair dry for another 5-7 days before I attempted sanding again. Once primed, the repair disappeared and it appears rock solid. Heck of a tip.

You can lead a gift horse to water, but you
can't look in his mouth.