If you dont care about doing this the proper way, you can always ask a friend or FC-mate to do this content unsyched with you.

What does that mean?
It means that you enter the duty with your current party straight away, ignoring the people-requirements for it. You'll also keep your level, so instead of being syched to 50, a level 70 friend would stay at 70. You are giving up all drops from the mobs (in most dungeons/trials there arent any intresting drops straight from the enemies anyways; chests are staying though and you'll get that loot - except CM doesnt has any, anyways) and all experience you would have gained (considering there are more and better ways to get exp than those dungeons... small price to pay).
You'd basically be avoiding queuetimes and if you can find a nice and patient enough person to go through with you, your run is gonna be a lot more pleasent than it ever will be by using the DF. I'd offer to keep you company, but sadly we're not on the same datacenter.

You enter content in this unsyched fashion by clicking on the little gear-icon in the top right (? or was it top left?) corner of your DF-window and put a check on the unsyched-option.
This might come in handy a few more times, for example when you want to do old Ex-primals and the like - I would highly recommend to just unsych them or at the very least form a party of your own before. Somethings are best not done with the DF.