i did modern studies and for all the topics i memorised my point and examples. its vital you know your points and try to pick evidence that can be used for different points and aren't specific to one. for the explanation, as long as you know all the content well and actually understand, is relatively easy to make up on the spot.
for the source questions, memorise the structure and stick to it 100%. and make sure you are confident in picking out evidence quickly. in my exam last year i didnt have time to highlight the paper so i just picked it out as i went. AND MAKE SURE UR FAST !!!!! my friend last year, who always got As, didnt finish the paper.
and always make sure to answer the question obvie