Headliners.....I use the same large head wrapped in a clean terry like the carpets. Spray a little diluted apc on the terry, let the steam get it "super heated and cross hatch like the carpets. As for damaging the glue, I have not had that problem. Obviously you don't want to spend too much time in one spot. You'd be surprised how quickly grime comes off, just a few back and forth passes and it's gone. The real beauty of the vx5000 is the dryness of the steam. Cheaper units have wetter steam. I don't remember the actual number but I think is was over 90% dry. that's why it will work so long with suck a small tank. I know "dry steam" sounds weird but that's what they call it.
It works because when I finish an interior detail it's already almost dry. If I use the extractor it could be hours depending on the weather.