Hi Zach,
I'm prior service USCG, from 2004-2012. I graduated OCS class 01-04. When I joined there was a program for prior CG enlisted that guaranteed a flight school slot but that was the only thing even resembling what you're asking about, and you had to apply for this program while enlisted (I believe E4 or higher) and obviously you had to have a degree and also get through OCS. I did the flight physical in OCS not at MEPS. I was not prior enlisted so I competed for a flight school slot with the other CGA and OCS grads plus the O1-O3 active duty JO's in the fleet who were already commissioned. I got a slot in OCS, probably because I already had my PPL and about 100 hours of C172 time, which also allowed me to skip IFS and start primary sooner; this should all also apply to someone with your experience unless things have changed significantly. Right now the Coast Guard and pretty much the entire military is so hard up for pilots that they're granting a lot of medical and age waivers that were unheard of when I lateral transferred to the USNR in 2012, so unless you're 40 years old or have diabetes you should be good to go in terms of getting a flight slot either in OCS or shortly thereafter when you're either on a cutter or a shore tour at a sector. Seriously, don't sweat getting a flight school slot. It's not hard right now.
What is your eventual goal besides becoming a naval aviator? My advice to you is to only go into the Coast Guard if you are willing to fly one airframe your entire career, do a lot of SAR in IMC with no combat deployments, and go to exciting duty stations like Air Station Detroit. I have no hate for the CG but I transferred to the Navy as a senior O3 in 2012 because at the time the CG was broke as a result of sequestration and it was ugly, very low promotion rates to O4 (<50%), severely restricted training budgets, etc. but the USN/USNR were in much better shape with more opportunities. I did a lateral transfer within my year of rank group flying C40's in the USNR and put on O4 just two years later while more than half of my original OCS class who were still in the Coast Guard got passed over for O4 just because of the Coast Guard officer corps' atrophy during that period from 2011-2016.
Being a Coastie has some advantages. You can spend your entire career in Michigan, flying 65's between the two air stations there with some shore tours in Detroit, Traverse City and SSM. I use Michigan as an example but that also applies to Florida, California and Alaska off the top of my head, each of which has multiple CG air stations and shore billets. I have old OCS buds who literally have spent their entire careers doing this which is great for family life. But there's also a lot of negatives. The USCG is the smallest service with the smallest officer corps. EVERYONE knows everyone, literally. When times are good and the service is expanding (or, as is the case right now, when officer attrition is high because the civilian economy is so strong), it opens up a lot of billets and opportunity for advancement, but every time there are budget cuts, it hits the CG three times harder than the Navy or Air Force and a lot of good people including pilots get passed over twice for O4 or O5 and either get forced out or quit. The USCG is the only branch that doesn't have a substantive reserve aviation program so if you do decide to go reserves. you'll be forced to go navy or air force like I had to. And, while it DOES happen, it's not easy to go from rotary to fixed wing or vice versa in the CG, so you will probably spend your entire career in one airframe.
If you are going USCG because SAR looks fun but you also want a civilian airline career, bruh, DON'T DO IT. You can do the same SAR on USN 60's at Whidbey Island (just for example) and you still have so many opportunities the Navy offers that will never be available in the CG, like aircraft carriers, living in Japan, etc... Or if you don't care about the SAR aspect and want to go fixed wing, please consider that you'll build more time flying a P8A at a VP than you will flying an HH130 at a CG AIRSTA and the P8A time will be glass TPIC in a shiny jet that is basically a 737-8. When the USCG retired the Falcon just a few years ago it basically became a helo operation with a few fixed wing turboprops (C130's and C27's). The Navy has exponentially more aircraft, billets and opportunities for selection (promotion potential). When I was in zone for O4 after transferring to the Navy, the OOS for aviators was 80%, compared to 55% in the Coast Guard. I just got picked up for O5 and my OOS was 20% higher in the Navy than my Coast Guard buddies, mainly because the Navy is huge and the CG is so small it gets much more competitive than the DOD services once you are a LT.
Anyway, I hope this helps you. Don't worry about flight school. If your heart and soul is with the CG, given the background you already have you'll get a slot while in OCS as long as you are medically qualified and I'm sure you'll get to skip IFS. I loved my time in the CG and I had a great time flying in Alaska. Anyone on here who was a SNA (Navy, MC or CG) can answer any broader flight school questions you have but if you have any CG specific questions don't hesitate to ask. I don't post here much but I plan to more often.