So you are looking for best practices? Do you want a list on things to do?
As grumblethorn said: it's a nightmare, for a multitude of reasons. There is no "easy" or "right" solution, and there is a lot of work involved.
Because frankly companies hire for optics nowadays, and the "IT security" field today is filled with people wanting to make good money, and businesses on the other hand wanting a "stamp of approval" to cover their ass. May god have mercy on you if your PKI is handled by an external contractor in India.
This led to what Bruce Schneier termed "security theater", so a big part of corporate IT security is now producing a lot of paper and doing the "compliance dance" to cover your ass. I know, because I have helped produce that paper. Fuck trees, I guess.
PKI itself is deeply flawed, especially when handled sloppy, and certificate revocations and their distributions are a constant pain point. But it's the best we have right now, and no one came up with a better solution yet. Probably because there is no real pressure to invent a solution, a.k.a. "it's good enough".