How to activate strength double buff or healing double buff?

I’m specifically trying to figure out how to activate Fritz’s strength double buff

Apply a defense buff to said adventurer. It then triggers the doublebuff as stated in the description which can be accessed by tapping the ability.

You may also not have it unlocked yet, so you would need to promote Fritz to 5*, unlock the 5th ring, and unlock the ability in the mana circle.

I know, but I don’t want to replace H!Elisanne with Ryozen just to buff Fritz’s defense. Are there any other ways?

There is no other way to trigger a doublebuff other than using a defense buff, but I doubt triggering it is needed.

Hope, Jeanne D’Arc, the new Siren, Last Defence wyrmprints.
Idk about Siren yet but the rest probably aren’t worth it.