Live Rock out of Water
 

How long is it possible to keep live rock out of the water without killing off the bacteria? I'm wanting to epoxy some live rock to some new cycled "dry" rock, and will need the rock to be out of the water for up to a couple of minutes. I figured I could spray the rock down with a water bottle filled with the tank's saltwater if needed. Thank you!

You'll be fine. Think of all the life that's on live rock when you order it, and that's after spending a long time just covered in damp newspaper.
You could also do the same, place some newspaper over it and spray with water.

The surface of live rock is only the surface. Life goes clear to the heart of it. Perfectly safe.

I have had my rock out of the tank for over an hour while I was doing a major overhaul. As long as it doesn't completely dry out, I don't think you will have any issues with losing your beneficial bacteria.

It's the micro sponges in the periphyton that you lose first; they don't like to touch air at all.

As long as everything is damp, including sponges, it should be fine fo rthe amount of time it takes fo ryou to epoxy, glue or drill stuff. I've used a spray bottle with aquarium water like you mentioned as well as wet towels to keep stuff from drying out during aquacaping or moving.

You may see some short term die-off of coraline algae, or some other superficial coatings, but it will all come back.

Before the days of dry rock, live rock used to ship to LFSs packed in wet news paper. All kinds of stuff survived...sponges, coraline, bacteria, algae, hitchhikers, you name it. After some cycle time to address the die off, it was full up.

You'll be fine