The more important thing to any paint work is cleanliness. Before any filler or primers are applied, after sanding and before any top coats, a good Wax & Grease remover solvent is critical. I use 3 kinds, Acetone, Duplicolor's Wax & Grease Remover and Pro-Form's Final Wipe. I put Final Wipe in this handy sprayer and use it before priming or top coating anything:
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Here are all the grille peices are done in Trim Black:
And the pieces going back together;
