I bought a cheap (junk) new Chinese valance panel it has mounding brackets SPOT welded to it. The spot welds left dents what is the best way to fix it besides throwing it away? I was going to use the GREEN spot putty but I have heard it should be ground down and the reprimered first? Wouldn't you want to bondo the bare metal then primer it?

I would give it a little grind in the spotweld area and then would spread a litle fiberglass and sand that down. The fiberglass will take care of any pinholes that might be present.

You're referring to the glass paste, right? That's what we used over the welds. Even though bondo and glass are both polyester based products, the bondo uses clay and other types of powders to make the paste, which can absorb moisture. The glass paste won't.

All replacement sheet metal takes a bit of massaging, so to expect anything more, regardless of the source, is futile.