I just brought a new newly constructed house and the garage floor was build a few months back but it did house construction material for the builder. Do I need to etch the surface or can I just clean and paint the epoxy on top ?
In a brand new situation I'd agree that the etching can be skipped, however you void the Kit Manufacturer's Warranty by departing the full instructions. If you're painting for a certain look, then the epoxy paint kits are the only way to go.
If you're just looking to remove the dust tracking, then you may actually be in luck because the contractor didn't seal the concrete. I say in luck, because you could then use RadonSeal as your and a permanent sealer to get rid of the floor's dusting and ability to stain...it's wonderful stuff.