AaronE,
If you want to stay in the Meguiars line-up, their D300 compound is also supposed to be very good, little to no dusting and much more user friendly! Not quite as much cut as M105, but a lot easier to work with.
The M105 can be tough, tougher than it needs to be to work with. It is NOT SMAT (abrasives that break down during polishing), it has a relatively short working cycle, and if you don't remove it quickly, it becomes a battle to get off. You may want to consider starting with the Megs D300 all over, then, if there are any remaining swirls/scratches, hit them individually with M105, Finish with M205 all over and then wax.
Or, try the BOSS Fast Correcting cream. I've been using it lately and I LOVE this stuff. I too have a big black vehicle (a Caddy). The BOSS Fast Correcting Cream has a long working cycle, virtually no dusting and wipes of easy and clean. Furthermore it IS SMAT abrasive technology! What a game changer! Do some research yourself on the BOSS line-up of correcting creams. I promise, you will never want to go back to the "old school", labor intensive, M105. Not to mention the frustration and confusion trying to navigate the Megs product line!