If you search my old posts for grille restoration, you should see a whole write up with pics.
Use good blue masking tape and Rustoleum black semi gloss spray paint for the outer metal grille. As for the Chevrolet letters, I originally hand painted them, but it kept chipping off, and was really hard to stay in the lines. Brothers sells nice vinyl letters that go right inside the indentations. I bought those, and it looks even better now.
As for the inner plastic grille, paint the squares with Rustoleum spray paint for plastic. It should be a silver/gray metallic, regardless of what you've heard (that's how a '69 is anyway, but for your '70, refer to the bottom pic). The edges above and below the metal bar that says chevrolet should be black, as should the corners by the headlights. As for the '70 vertical lines, I'm not sure since I have a '69, but you could probably mask and hand paint them with a brush.
Some close up shots of other grilles for reference
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