How do you itemize against true damage champs?
certain champ i find very hard to itemize against
for example
passive does true damage, and his barrels ignore 40% armor, and his ulti does true damage if upgraded
sure i can stack HP or try to build full damage just to try to kill him faster. bu the issue still reamains.. im just not sure how to build vs him
other champs like 
also ignore a lot of armor and his ulti also does try damage, but at least for him i can kite with slowing effects
its champs like 
so far the only thing i can really think of is hp stacking / slow
as ap:
for hp and slow and damage
for passive and and damage (and armor because most true damage is from AD champs and it helps vs thier other abilties)
for active shield
or full damage route
As bruiser
to help kite and HP
for HP and armor
for hp and shield
for hp..
or full damage
and I'm not sure if
passive will make the true damage bleed or if 
will reduce the true damage
does ne1 have any other ideas of good items i can build to help counter true damage i haven't really though of yet?
and