NXT I'm not sure I would use on a beater. That's a good OTC wax for a somewhat looked after paint finish. I've used better synthetic waxes as far as last forever durability.
FinishKare 1000P high temp wax and their Pink Wax comes to mind. The 1000P in particular will have the car beading through a nukular war.
Which is ironic because for the low price they send you a 1 pound tin can of the stuff.
I would claybar the car first. Any OTC clay bar will work, I used to see a generic brand at Strauss Auto or maybe it was Autozone or Pepboys...I forget. Same crap.
Use the claybar while you are washing the c ar. This isn't concours afterall. Do a sudsy once over after claying to clear away any crap and rinse thouroughly.
Spray down the surface with quick detailer. Apply the wax to the damp surface.
let it haze. Spray the surface again. Then using speed not pressure, buff clean.
I use FinishKare
425 anti-static spray which gives it a teflon finish for dust to roll off. Essential product for dark colored cars. Autogeek.net has most of this stuff.
P.s.
Sealants are nonsense. A durable synthetic wax wil last months. Particularly on an enthusiasts car that is often topped off with a spray wax quick detailer. Sealants are just a product sold by car wax companies to get you to buy 8 step kits. Total nonsense. All you need is claybar and synthetic wax if you've got a beater car.