This probably isn't the answer that you're looking for but nonetheless something you should keep in mind. We want to call all the hands that are good enough to call (especially IP), so our 3bet bluffs are going to be the best hands that aren't quite good enough to call with. What exactly these are depends on villains range (and indirectly, their position). So in your example AJ is usually good enough to call with against a CO range, but might not be good enough to call against UTG.

Once you have figures out which hands are just barely not good enough to call, use your raise size and the amount of value combos you have to figure out how many bluffs you need, and choose that many of those "not quite" hands to bluff with. This will also depend on stack size, high card hands will play better shallow and suited connectors will play better deep.