You should look at encaustic painting which is painting with pigmented beeswax. It is possible that the paintings you have seen with a waxy finish are encaustics.
That being said, pure beeswax is compatible with oil paint and you can cover oil paints with it to get that translucent look. The paint may bloom a little if it is not fully dry but probably not so much you would have to worry about it.
There are also wax mediums that you can use with oil paints. They are a mixture of solvent like mineral spirits or turps, wax, and resins; pretty much the same materials you would make liquid mediums for oil painting with the addition of beeswax. These you can work cold mixed with oils, dry pigments, or as a top coat, and get that same translucent look. In my experience they work fine but do not have the same "solidity" as pure beeswax encaustics. They also take longer to set. You can find them searching for cold wax mediums, or you can make your own with the aforementioned ingredients.
edit: just saw your edit and pure beeswax is compatible with oil paints and both it and wax mediums can be used as a top coat. They will be more matte than varnish.