Make sure the scratching posts are exactly where the cats like to scratch. It has to be a socially prominent area, tucked in a corner just won't work for them. From let's at home you can buy sticky strips to stick on the sofa, they don't like the feeling on their paws, it's ok for a temporary repellant whilst they find somewhere better to scratch.
My cat chases string so I just got her chasing it and dragged it across to and up the post where she started to scratch.
We have indoor cats and they destroy our furniture. They don't seem to really use the scratching posts/carpet things we have provided (of course)…. Just wondered if anyone had any good advice re. something they might actually USE and prefer to our sofa….. Saw some funny thing that gets attached to a corner wall and wondered about that.