Using any wax is going to make it look at least a little better, however if you want to take care of scratches on a 8 year old paint job on a black car I'd suggest wet-sanding and buffing. That's what a professional detail shop would do to make it mint again.
You need a rotary buffer with at least 2 pads (one for the rubbing compound and one for the polish), the compund and the polish themselves (I'd suggest 3M), sandpaper 1200 and 1500, even maybe 1000 if you have some more severe scratches, a spray water bottle and some kind of final wax to be applied by hand.
I'd also reccomend masking off textured parts since compound on those is a pain to get off,
In brief the procedure goes like that:
1 - Spray water on the panel and sand it down with the coercest sand paper (say 1200), than do it again with the finer and then finest sand papers. When the water dries it's going to look like crap -- all white, like you screwed up the paint. Don't freak out, it'll be OK.
2-Apply generous amount of the rubbing (cutting) compound and rub it in with the buffer, and make sure you use the right pad. Also don't stay in one spot for too long cause you can burn through the paint. After you do the buffing the paint should look alive again but you may still see fine scratches from the compound.
3-Apply the polish, or "swirl remover" (whatever they call it on the bottle) and hit that with the buffer (use the right pad).
At this point it should look real jazzy.
Now you can apply a top coat of a hand wax of your choice.
Just remember to do one panel at a time and don't do it uder the sun on a hot day.
To do the whole car should take you about a day. Take your time and if you're not sure you can do it have someone at least show you in person or even do it for you the first time, cause it sounds easy and it is but it's always good to have had some practice before you do it on a car you want to make sure looks good.