If you wants an Armageddon device, buy the Meguiars G220 orbital and a couple of pads.. one for polish and one for glaze... and a couple of different grade polishes. I use Poorboys SSR1 and the slightly more aggressive SSR 2.5 but any brand you fancy will do.
The G220 is an orbital polisher so it doesn't sit too long on the same bit of paint. I find that with the SSR1 it's impossible to do any
damage to the paint.
Wash your car thoroughly and make sure there are no bonded contaminants on the paint by claying it. Clay is like blue-tak which you rub over the paint after lubricating it with some quick detailer or clay lube spray. You can get get any kind of clay you want (mild, medium, aggressive etc.) but for the first time, use the Meguiars clay kit from Halfords. You can't damage the paint with it.
Cut the clay in half and use one piece for the whole car. That should still be re-uasble in the future (and of course you have the other half still). The upper surfaces and the door bottoms will need most attention.
The polish the paint. Use the SSR1 (Autoglym SRP is about the same level of "cut") with a polishing pad and see how the scratches respond. If you need more cut, use the SSR2.5... but always use the lightest cut you can get away with. The G220 won't let you mark the paint, so you don't have to worry about it.
As mentioned, do 1 panel at a time so you can keep an eye on it and make sure you're happy how it's looking. Don't worry about removing every single scratch at this stage... it's really not necessary first time out.. just get familiar with the equipment and what it does. You can do the more stubborn marks another time.
Once you have the whole car polished and buffed off, use the glaze pad to apply the Black Hole. This is a surface dressing so it's not a polish, you don't need a cutting pad and you don't need to labour the application. Wipe it on lightly... let it dry, then buff it off.
The BH fills in the marks and swirls still present, so now you have to keep it from evaporating off. Use a wax. Again this is not a polish so you're only wiping it onto the surface (if you have Natty Blue wax, then no more than 4 coats are needed)..
Two is fine however..
Don't go mad with it and make sure you keep all products off the rubber and plastic trim as it dries "white" and is tricky to remove... otherwise the car will look much more splendid and most of the little marks will be gone. It will look a million times better, even if it's not flawless (so don't obsess over *every* scratch or mark... you can do them again later).
Finally don't go mad with the polisher. It's addictive but you have to remember that you're reducing the paint thikcness slightly every time you use it, so use it sparingly. I do my beast once a year (in the Spring).
You'll find that the clay makes the biggest difference to the "feel" and that the polish will make the biggest difference to the shiny-ness.. but Natty Blue is good stuff and will make the car far easier to clean next time. You won't need to clay every time either.. smoother paint just stays cleaner for longer.