How do professionals remove old wallpaper paste?

Hello Our walls are plastered with lime cement plaster and were wallpapered with non-woven wallpaper. Since we now want smoothly plastered walls, the old wallpaper must be removed. There is still paste underneath. Since the walls are rough, this cannot be washed off easily and would be a huge amount of work given the area. I also fear that with too much water it will run down the walls under the screed. How do the professionals do it? Nobody stands there with a small kitchen sponge and washes the walls. Are there machines for that? I had already thought of a steam vacuum cleaner. So the wallpaper itself is not the problem. I can remove it without any problems. But the paste.