If they are indeed etched, the spots have actually eaten through the clear coat. If you want to remove them completely you`re going to have to get the clear coat to an even surface which would probably be removing a dangerous amount of clear coat which could result in CC failure later on down the road.

Try the vinegar if you get the truck again or another vehicle with spots. If that doesn`t work then you can try to polish them out with the PC but don`t expect them to come out easily if they are etched. Some resort to wetsanding some water spots but I think that`s kind of extreme.

If you don`t feel safe removing the spots completely then you could cover them up with a heavy glaze/carnauba.