To activate the exploit, you need:

Equip the modified runes on your character, look for the ones with effects in blue background (these are the ones that work with the exploit).
I also changed it all to bosses relics, to make it easy to distinguish them (and prevent us from accidentaly selling them).
I left a varied combination of effects so you can choose what works best for you. Of course, if you want full power, you'll want to equip attack bonuses in all slots, but you can mix match with defenses and utilities as well.
Then start the expedition and immediately die 7 or 8 times in a row (the effects are not multiplied infinitely, the game limits you to 60 simultaneous buffs, so dying 7 to 8 times will reach this limit) either die to enemies in nearby camp or by dropping from a cliff (make sure to pick up your runes before dying again).
Finally, to reach maximum attack power, level up as much as you can and find purple or legendary weapons, with all the bonuses you will have active, some of them will reach 9999 attack power easily (assuming you started the run with enough attack bonuses).

Remember: do not use this online, From Software can release a patch to end our party.

Just a side note of effects without an in-game description:
AttachEffectName(8500102) = Gives you 60k at start of the run + 30k after every death
AttachEffectName(8330104) = Raises potency of sorceries and incantations (magic atack power)
AttachEffectName(8210700) = Raises resistance to all ailments