I've used that particular wax with good results, just as with other Meguiar's products I've used. What IS important for any wax to really work is to have good paint underneath it--this is where the extra work comes in for basic initial prep.
If the paint can't be brought up to a hard shine after buffing (I personally like the orbital buffers rather than the classic buffer), then no wax will make up the difference, but it will look better when done. What I've used to get things started was a particular Meguiar's buffing compoung (whose grit dissolves after a short time) and use it only as little as necessary. Then, after wiping it all down, follow that with their glaze to put the oils back into the paint. I discovered that letting that cure for a few days before another coat was a good strategy.
After the glaze is done, then I follow that with the straight wax product. Takes more time than with a one-step product, but it looks better too.
In cases where it's in basically better shape, using the old "red bottle" Meguiar's liquid was is a good starting place. It might take a couple of applications, spaced out over several days, to get things to where they need to be. Then the straight wax on top of that.
No easy feat. I also know how long those quarter panels, hoods, tops, and deck lids can be!!! But, when done, it'll be worth it. Just be sure that as soon as you start seeing primer bleed through, END of the cleaner stuff. Also, with the orbital buffer, use a towel-like buffing mit as with the thicker lambswool mits (as the high speed buffers would use), the buffer will just sit there and vibrate with the mit remaining stationary. I haven't used any of the foam ones, though.
For wiping, old towels work well. In the case of the glaze, buffing it one day and then buffing it the next day can make it shine even more (as more of the oils have dried from the initial buffing).
I've also observed that different colors have different durability factors on wax. Seems that black just cooks it off regardless of what it is, but some last longer than others.