Might be able to do it with one question like...
[spoiler='Identical twins, sort of']
Q: Are you a liar?
....The accurate truth-teller rightly believes himself to be honest and thus answers "no"...the inaccurate liar wrongly thinks himself an honest man, but nonetheless is compelled to lie and thus responds with "yes". These responses distinguish the two.
However, if the above is properly reasoned, I still do not know if the given explanation counts as a concise answer for the second portion of the question