It would be helpful if you let us know what parts you got that were trash so we can learn from your troubles.
I put the sandpaper and polishing cloth to pretty much every pistol i've ever owned.
I did the ejection port on my P32 and P7 and got them looking like mirrors. Likewise for the feed ramps. Kel Tecs really benefit from a good polish of the action, as they're typically very poorly fitted weapons from the factory.