Swiftcast + Stoneskin

[Anova]

It can be a very useful combo to use, especially in fights where you know the boss rotation. With a combination of adlo + quickened stoneskin + virus, it is possible to reduce Titan's mountainbuster to triple digit damage. It is supremely useful on tanks as the hp debuff and delay from ress is enough to wipe out most parties, or make it completely irrecoverable.

For those who want to practice it, consider beginning in Wanderers Palace for the 2nd and 3rd boss. They give plenty of warning when they're about to use their big abilities and you can stand still to concentrate on the timing, so it is a good boss to practice against.
Afterwards, Ampador Keep's demon wall also has a pattern where you will find the use of quickened stoneskin easy and useful. There's a set use for the boss, but it is also useful training for ad-hoc stoneskin to use on someone hit by the aoe. Once you're used to casting it on the run, you should do reasonably well on primal fights like Ifrit, Garuda, and Titan.