Ok some questions for you.
If your argent paint is flat or dull that is the way the factory applied it. DO NOT GET WAS NEAR THE ARGENT PAINT IF IT IS FLAT OR DULL. It is it shiny then the previous owner painted the way they wanted and you can polish and wax it.
As Autin Vert, Greg has stated washing these cars with a hose and lots of water is not a good thing. The water gets inside the doors, quarters, cowl, around the tail lights and feeds your number one enemy RUST. Good micro fiber towels and clean water is all you need.
If you feel the paint with your hand, especially on the sides, and it feels like there are little knots or bumps you need to clean with a tar remover to get road grime off. If you try to polish the car without cleaning you will add scratches from the trash stuck to the paint. This will also remove the old wax. Mequiar's is a well known and respected supplier in the U.S..
http://www.meguiars.com/en/automotive/products/#Clz22BzRoWULQejY.97
Plain old kerosene works to get the tar off if you cannot find anything else. Prep Solvent used before you paint is also a good solution.
The next step sounds a little strange but really does a great job of getting all the trash stuck to the paint off. Use a Clay Bar and spray included in the kit. This pulls the small pieces of grit and trash from the paint surface into the clay bar. If you do a small area and feel before and after you will be amazed at the difference, soooo smooth.
http://www.meguiars.com/en/automotive/products/g1016-smooth-surfacereg-clay-kit/
Here is a short video showing the process for clay bar.
After the clay bar I wipe down with wet micro fiber towels and then use Mirror Glaze to remove small scratches and buffing swirl marks. As Greg said a good dual action or random orbit buffer will be your friend. A side grinder with a buffing pad is not to be used. A buffer has variable speed and runs slower than a side grinder. NEVER MIX YOUR BUFFING PADS. MARK WITH PERMANENT MARKER ON BACK WHAT POLISH YOU ARE USING AND NEVER USE FOR ANY OTHER. If you have used for coarse polish and even after washing go to finer you will scratch the finish. STAY AWAY FROM YOUR STRIPES AND ARGENT PAINT WITH THE BUFFER. Do areas around them very carefully by hand and do not get polish or wax on the argent paint. You can put wax on the tape stripes but do not buff. Use a soft tooth brush to remove any buffing or wax residue in the cracks and along the tape stripe edges.
Always keep your polishing towels and pads clean. One piece of grit will just add hundreds of scratches on the buffing pad or towel.
Watch the videos on the Mequiar's web site.
I always finish off with a good Carnauba paste wax. I have used this brand for over 50 years.
https://www.amazon.com/Collinite-Paste-Fleetwax-885-12/dp/B008KPDA1S/ref=sr_1_6?ie=UTF8&qid=1478703792&sr=8-6&keywords=collinite+boat+wax
There should be no reason to wax your car but once a year in the spring. If you do not use soap and water to wash the wax stays on. If you apply too much wax then it just smears and the finish does not look as good.
INTERIOR
On the interior on thing I am personally against is ArmorAll. It contains silicone and that is bad to have around your car. Over time it builds up a film and starts to look milky and you cannot get it to look good again. Again unless the interior if very dirty just a damp micro fiber towel to catch the dust. Some do take a little mineral oil and apply to the vinyl and wipe back off to keep it soft. The painted surfaces on the interior should not be waxed.
There are hundreds of waxes and polishes. I would stay away from any wax that is not a paste and Carnauba which is a natural wax.
Again if your hood has shiny paint for the Argent then you treat it same as the body color but if dull or flat be careful.
I once detailed a friends 1965 mustang that had original paint. He was going to have the car painted and I convinced him to let me detail it. You could see your reflection in the Red paint everywhere when finished. He took it to a show and won first place and he was going to paint the car when all it needed was some TLC.
If you cannot get the clay bar where you live I would be glad to ship if they will allow the liquid to be shipped which is sometimes an issue. It does not have to be the brand I had linked.
I know you are excited about your car and getting a black car to be perfect is a difficult task. I have a friend with a 66 GTO that is black and you cannot find a scratch anywhere and he does not even use wax at all. Has never washed the car with hose either.
