Now that I have an empty realm disposed of its money, I decide to re-populate it for long-term stability and my personal convenience. I need about 100 courtiers for all the counts that I want, so hopefully it won't be too expensive.
It's not. However, that's still a waste of money, so I acquire the courtiers in a different way. I take direct control of a province and its bishopric. I generate a new bishop using the right-click menu, imprison the bishop, and then banish him. The banished ex-bishop actually arrives at your court, meaning you can have as many free courtiers as you want. Oh, and you gain a net +5 piety each time you do this. In fact, the free courtier is a side effect. The main point of this trick is that is gives you
infinite piety. Maybe I should have mentioned that first.
I use the courtiers to repopulate the realm with counts, each one owning 2 counties. This is about as much as they can take before going above their demesne limit, which would cripple their troops if exceeded.
All of them absolutely hate my guts due to tyranny, of course. So how do I handle that? No matter how strong I am, enough counts will form factions against me and rebel. The solution is actually simpler than it seems.
They can't revolt from prison

. Now it's almost time to do some actual combat for the first time in this AAR. I use my money to purchase some mercenaries.
But before anything else, I think I'll go ahead and swear fealty to one of the pagan tribes in the East. Let's go with the Pechenegs, as they look the least scary.
You might be asking why the heck would I do that, but it was all simply so I could use this decision.
So I can pay 200 prestige to change my culture to the Altaic group. This is utterly useless for our current situation, but will be essential later on, so it's best to do it now. Previously I gained prestige by creating duchies, essentially turning ~200 gold into 200 prestige. Even though we have a lot of money, it's not endless, so this method is out of the question. We've managed to cheese our way into vast lands, vast money, and infinite piety, but prestige so far has remained untouched. Is it the single pure attribute which we cannot exploit? Well, actually, no. It's not quite as bad as piety -- it's only
practically infinite

. You see, winning wars give you some prestige. Specifically, you gain 50 when you defeat a rebelling vassal. We also know we can trigger a vassal to rebel by failing to imprison them. This would require you to actually fight the war and defeat them, of course, but when happens if you do it again? And again? to the same holding, which had no time to replenish its garrison?
They have 0 troops. That means you win the war within a single day, with no casualties, using any number of soldiers you want. In practice this means you earn a 50 prestige each day. After 10 days you get 500 -- a whole year and you could hypothetically get 18,250. As it happens, prestige will matter a lot to us later on, so I use this trick whenever I have spare days that don't require peace. Now, after using a faction to gain independence from the Pechenegs, I declare holy war against the nearby pagans.
The purpose is to gain control of a slavic-religion province.
And the purpose of that? Well, Rajas of India introduced some new useful decisions. One of them is to change your character's religion to that of your capital province, at the cost of a steep 1000 piety. But we have infinite piety, don't we?
And so we become the pagan, Altaic-cultured, Duke of Holland (of the Karling dynasty). This is the very the apex of the strategy I came up with, and the goal we were aiming for since the beginning. What abilities does this give us? First, we gain a new wonderful CB to use against pagans.
Second, we get this even wonderfuler CB to use against all non-pagans, the infamous tribal invasion.
These CBs are the reason why pagans are traditionally known as the best WC candidates. Holy war, the next best reliable CB, targets duchies, which go up to 8 provinces. For comparison, both subjugation and tribal invasion target whole kingdoms, which go up to 39 provinces. The Magyars are considered overpowered because they have access to tribal invasions and start with huge amounts of troops. But now our army dwarves that of the magyars, we hold far larger tracks of land, we have a superior pagan religion, and all the while we have the same overpowered CB. Life is great.