You always want to apply a wax or sealant, anybody's wax or sealant, in a very thin coat. Thin coats dry faster, avoid streaking, are easier to remove, and waste less product. I've waxed a Nissan Frontier crew cab pickup truck using a D/A polisher and a 2 oz sample pack of Meguiar's NXT Tech Wax. Yeah, that one was a stretch, but I did it.

Basically, if you've ever seen a black car with a coat of dried wax on it and the car looked more white than black, there's probably enough wax there for 6 cars. If you apply a coat properly, ie very thin, to a light colored vehicle you should actually have a hard time telling where you've put it and where you haven't. Only the diminished gloss from the wet, freshly applied wax will clue you in.