This is a very big topic, I will start by redirecting you to a very useful site/article: Mastering for Vinyl from Recording magazine.
Also I would like to state that I'm not a mastering engineer, I'm a mixing engineer only working with analog gear, so I'll try to tell you what we keep in mind when going for vinyl. The article is far more detailed and informative but this might bring you in front of many unknown terms that you'll have to figure out in order to completely grasp the ideas.
First of all, you refer to a post mastering process.. I think that you mean mastering process as the chain goes, mixing -> mastering -> post-mastering on the vinyl cutter. So taking under consideration that you don't know a lot about analog/vinyl mastering I think it's good to clarify that there is a post-mastering process but probably not the one you refer to.
So let's dive:
When you master in vinyl you have to understand that there are actual mechanical limitations that have to be addressed in order for the process to be successful! The cutting head which is a part of the cutter creates the actual groove when the signal is fed to it, so it's a mechanical moving part with friction and a job to do!
I'm referring to this now as it's a general way of thinking when going for vinyl, I will come back and refer to mechanical limitations.
Also there is information, a digital mix, or a mix on a tape will contain far more information than the one that will be played back by the vinyl (limitations again). You have to keep in mind that the vinyl is not going to tolerate bad phase issues, insane frequencies (lo or hi) and overcompressed material.
Think about the cutting head laying down your wave form, trying to create the groove, if you have a heavily compressed continuous sound you already provide the cutting head a moving constant. That will result to a bad cut, the reason the dynamic range should be lively is that the cutting head will follow that dynamics and produce a healthy groove!
Also, another very important topic is bassy signals. Signals with heavy bass or bass frequencies should be centered in L-R at all times!
On the phase side of things you should always be close to +1, don't try to go with expanders and imagers and stretchers or whatnot, you are in vinyl!
Now let's talk about speed. Vinyl cannot tolerate peaky transients! Imagine the waveform (groove) going vertical on a snarehit after some silence, there you have the needle jumping off the groove! So it's a No No.. (mechanical limitations) . There are some ways to address that issue, some use de-essers, some others just compress the hi's.
It might seem a world to you at the moment but keep in mind that there's an engineer behind the vinyl cutter. So, he can correct some bad decisions with his cutter tools, because the actual cutter has audio processors integrated, one of those (as we talked about speeds) is slew rate limiter. The slew rate limiter will not let aggressive transient peaks OR aggressive db drops (they are practically the same thing as you'd understand) pass to the cutter head, this though if needed in extensive amount can produce some transient smearing and some general distortion of the sound (I myself find it very nice but that's another topic).
To make you feel a bit better, there's always a test press sent to you by the cutter and then decisions are made and maybe changes! If the mastering is very wrong though, I don't know how much of messing around you'll be able to do.
So keep in mind of the process, there's a way this whole thing works but it's also, in your hands, the level you want to achieve.
Analog technology seems to be very attractive at the moment for various reasons, if you ask me, it has soul, and every machine, every decision, every print is there for the listener, and for you to make you proud.
Also it sounds amazing.
On the other hand, many people don't get what the fuss is all about. Others start warm and then go cold when they learn about what's going on.
Truth is that for digital mixers/master-ers(!?) seems like a forgotten art. Keep in mind that this was an actual heavy industry, feeding families!
So now some people believe that such a heavy industry can run at the level that once did, with 1% of the needed resources, human-wise and money-wise.
To start summing up the mess:
Start by understanding that analog technology dictates a workflow and a way of thinking when you go on about it! you are not completely free, but you are not alone either.
Try to get in contact with people that work with analog gear, or contact the guy who's gonna cut you the vinyls and ask him to introduce you to his mastering engineer, otherwise just start googling and I'm sure you'll find someone to take your precious dollars and make them vinyls! :)
Now... if you are ready to dive into analog technology and analog mastering yourself, get ready for at least 2-3 years of hard learning and understanding of alien concepts that don't even exist in digital!
So my advice, do your job as an artist, afterwards, stick with the professionals, in the meantime try to learn! at all times keep your mind and ears open!
Good luck!
PS: This will come in handy if you come across vinyl sound, noise reduction, hi frequencies pre-emphasis and stuff. Try listening to Master Of Reality by Black Sabbath in digital and vinyl. To me in digital the album is a bit bright, in vinyl it sits right where it has to! So this is an actual counteraction to make a fresher sounding vinyl than the others fighting through phono amps, bad pickups and a whole other world of obstacles.
