Hey there!

At the moment, I'm learning Poets of the Fall's "Carnival of Rust", but I'm having some serious problems with the barre switch in it. Can anyone give me some advice on this?

Try switching between the A minor and E minor shape. Those are two very common shapes which shouldn't be too hard to get a hang of.

Also, what really helped me to switch quickly between shapes: when you practise the switch from chord A to chord B, do it slowly, but be sure to move all your fingers at the same time. Repeat until you can switch quickly and cleanly.