I am curious as to exactly how this works. I read posts where people talk about finding their Barrier sources etc... I know that there are different items in the games that can be used for Barriers etc... But, are they available to any character? It just seems to me that the way people talk about it is that there are specific sources for each character, and it changes. So item x may work for me, but, doesn't for the next guy. Is this the way it works or is it just once you find a source you can use it repeatedly for a number of different characters?

There are some wands, etc. that give aura shield and barrier that are available to any character. The ones that are specific to a character a sleek wands. As in sleek black, sleek amber, etc. Those have a specific source for a specific character. That means if you find one in mage corpse in random area with character A, it may not pop for character B. However, anyone can use these sleek wands... So you can always use the "enemy corpse" source, which is my personal favorite.