I've never competed but I've had people ask if I do. I used to prep my father's black Vette for shows, but that was when I lived in KC. Now I'm too busy to get in Concours or audio shows, but again as a semi-pro in this field who takes on a few details a month when the weather permits, I'm going to give you some advice learned the hard way. Simply put, technology has moved on from 3M/Megs and the Porter Cable DA.
With regard to the Porter Cable DA polisher tool. I've got one, we all do in the field. Its the grandfather of DA's, and deserves special recognition for that. But tech has moved on over the years. I went from the PC (and when it failed, to a Harbor Freight copy which still soldiers on, amazingly and serves as my backup), to a Griot's GG6 which finally failed (but has a lifetime warranty so I need to ship that out sometime soon), and then to the badass and recommended Griot's BOSS (Best of Show System) long-throw polisher. Here's the facts: on a regular 3-round detail session (compound, polish, seal), I've been able to take a 10 hour session down to 6-8 depending on how bad the paint is. The machine was a great value, has a lifetime warranty which I'll probably never use, and has paid for itself in time saved about 5 times over so far. I don't want to bore you with "detailer" details (heh, joke), but basically a long-throw does what it says, it creates more correction in less time by using a larger orbit of the pad. When paired with pads that are good with this like low profile ones, the performance is insane while still being safe on the paint. I've taken black paint that has turned GRAY due to swirls and scratches, and brought it right back, in 2 to 3 passes with a microfiber low-pro pad. That type of damage used to take forever, or you'd be forced to go to a rotary and then repair the hologram damage with a DA like the PC unit. Well, rotary tools can do severe damage with the slightest of errors or even just being unlucky (like running into a panel that the factory painted a bit "off"), so I no longer even touch mine except to polish bare metal!
For reference, I used to use 3M and Meg's professional stuff too. They are the decades-old mainstays of the job. Again, tech has moved on. The BOSS creams are king for me. I held off buying them when I bought my BOSS polisher, because again, cabinet chock-full of products I figured I had what I needed. That includes 3M, Meg's 105 and 205, the Ultimate stuff, Chemical Guys Optical line from 32 through 38, and so on. Well I found myself at odds trying to fix a particular black car (a Camaro) that was just killing me. The gray one that was actually black. As a last-ditch effort, I ordered the whole BOSS cream sets, and the BOSS (this would be the System part of the acronym I guess) microfiber pads, the strongest pad type. This pad along with the BOSS fast correction cream finally broke through the damage, and left me with a glass-smooth surface. The killer was it not only performed the best I've ever seen to remove defects, it didn't dust or dry out so I wasn't chasing the clock with the product or reaching for my blow gun to dust off. It just aced panel after panel, and blew my mind while saving me hours.
So yeah, bottom line: tech has moved on. My recommendations stand.