The most important things are (and some additional things I now remembered of):
- Grind a general without any gainable traits at the start because of the penalty for each earned trait (personality traits are fine, though ofc you want personalities that gives you more attack skill factor *refer to wiki for details).
- Stop the battle once every 24-48 hours, otherwise the diminishing xp will really hurt
- If the AI joins the battle, you might want to look elsewhere to grind. The time when you are still in the reinforcement queue does not contribute any xp gain
- Keep building up your template to a 40w or something. More manpower means more xp i think
- Stop grinding on a trait once it is at 99%. Only get the remaining xp when you are ready to get all of the traits you want.
Other than these, it's just keep bashing your head into a terrain until the general levels up. I tried it numerous times (more than I will admit!) after I learnt of general grinds before getting half decent. The unplanned offensive modifier is helpful because the -90% attack and defence do not affect your xp gain, but prevents your enemy troops from losing too quickly, so you can focus on exactly one tile to attack over and over.
For example, the border tile between Guadalajara and western Aragon is the prime place to grind hill fighter because you have 5 tiles to attack onto 1. With the modifier, you can attack it over months and the enemy wont need to retreat. Without it, they will probably need to in weeks. Then you are forced to wait the AI to move troops into it and allow you to resume grinding. Even worse is the nat Spain AI will take the tile for you, and you need to find another tile to grind.
This is a general I get in the SCW (EAI enabled). I think he is level 5 when it ends. Notice all the traits I have is all gained by the time SCW ends, and he gains nothing else since (that reduced ~20% xp for every trait already gained is really brutal)
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