EX Roulette, High Level Roulette, Trial Roulette.
Then run a few extra dungeons. You'll cap in 3 days even if this is ALL you do.
Also yes helping people through old content such as t5 or the pre-shiva primals is a good way as well.
Also farm parties are a great way if they're actual farm parties and not a group of meatbags that managed to survive a single run and think they're good enough to farm. (I know that sounds elitist but really you should make sure you know exactly what you're doing before you join a FARM party)