You can trim holly bushes waaaay back. (Same with yews and rhododendrons and those are separate videos coming soon). Don’t worry too much about exactly where to cut. It will jounce back. I recommend doing this by hand and not using electric hedge trimmers. That’s what got us into this mess in the first place. Use loppers and make clean cuts. If you’d like more specifics about various types of plants—especially hydrangeas!—you can get my guide at this link: https://linktr.ee/youcandoitgardening.