I...have no frickin' clue. Bit by bit, I presume. Though, most of the "Epic" feats in the ELH work better as actual feats for pre-epic characters, and some are just plain worthless. And that goes without mention that Two Weapon Rend got downgraded but otherwise everything else got untouched.
So yeah, it's quite the bit of work, and it would be too fast to say exactly how I'd deal with it. In fact, the idea of E6 sounds mighty fine, except it'd be E20 ;)