For plants on plank type of mounts, I've had good luck with soaking them for 10 mins or so and them scraping the roots off with a credit card.
I cover most orchid roots in my vivarium with live moss. I think it just looks better. Vivarium shops (such as Josh's Frogs) usually carry types of hypnum moss (or "sheet moss") and I've had good luck with those. They aren't as water retentive as sphagnum and don't need to be as wet (they will rot if overwatered) so I find them ok for orchid roots in very high humidity. Haven't had any root rot issues. The only thing with hypnum moss is that the strands are pretty large and so if you have micro/miniature orchids, they can easily take over. I've also surprisingly had great luck with Christmas moss from aquarium stores. They grow very well and extremely fast above water as long as they have constant moisture. They also aren't as water retentive.
Live sphagnum is pretty easy as well and I get mine on Etsy from a seller called "TinRoofTreasure". In my experience, it doesn't grow that fast, and as we all know, is very water retentive. I only have a little patch growing on that bulbo in the very middle.
I also will bring home moss that I find in damp parking lots and such and throw them in case they like it. Some have taken off and some rotted away. I can't 100% recommend doing that in the case that you bring in pests or diseases. I've been lucky so far to not have that problem!
Here's a pic of one of my tanks with all the diff types of mosses I talked about