Anecdotes are your best friend and they don't even have to be real(which is the best part). Rhetorical questions are also a staple of discursive so would recommend. So just find a third technique which you vibe with.(allusions and extended metaphors and recurring motifs come to mind.) Also make sure your topic is very clear from the get go, It shouldn't become clear halfway through the piece ya feel me? Also I don't tend to have a set limit of ideas but yea 3+ paragraphs make a good discursive in my opinion haha.