^Just to build on this: the reason it's considered unconventional/'wrong' in most teachers' books to simply use one character per paragraph, or indeed have your whole essay centring on one character, is because you're expected to be
building up to a conclusion about the text as a whole. If all you talk about is Eilis' migrantory journey, you can't then have a sentence in your introduction like 'Toibin's
Brooklyn explores the nature of longing for a place that offers identity.' Without a substantial base of discussion, you'll make it impossible for yourself to say anything on that 'big-picture' level (ie. usually sentences that include the author's name and deal with big concepts like how we interpret the text, or what messages are contained within it.)
This is probably too late for your SAC, but as something to consider for later in the year:
let the prompt rule the discussion. Assessors are more impressed by people who can say something mediocre, but relevant than they are with people who churn out pre-learned material that sounds neat, but has nothing to do with the topic. A lot of schools will give you very standard, easily accessible prompts for the SACs (eg. 'Discuss the importance of journeys in
Brooklyn' or 'Eilis belongs more in Brooklyn than Enniscorthy. Do you agree?') but VCAA can go in any direction they please. So once your confident in your textual knowledge, it's worth spending some time on how to pick apart prompts and come up with a contention and essay structure than allows you to answer the question and showcase your abilities
