No you'd never use sealant after a wax.
Usually you use either a wax or a sealant. They tend to give different optic effects.
Sealants tend to give a more crispy look, a colder shimmer. Sealants tend to last longer.
Waxes tend to give more of a wet-look, ideal for shows or those who demand the most from the aesthetics of the car, for example a show or concourse car, however waxes generally don't last as long and can be harder and less forgiving to apply.
What a lot of people is apply a sealant base and then apply a wax on top of that. Most sealants are solvent based and would all but remove the underlaying wax, but the sealant tends to bond better to clean, unwaxed paint..
So you would first apply sealant, allow that to cure and buff it off and then you would apply a layer or two of a show-wax for that wet look..while still maintaining protection due to the under laying layer of sealant.
In short, never put sealant on top of a wax, it's bad. People die.
