Is a person sinful for inciting his friend to break a bus window by throwing a stone at it, and how can one absolve himself of that?

The fundamental principle is the innocence of individuals from obligations until an obligation is proven to exist. Therefore, nothing is binding on you as long as you are not certain that your direct action of breaking something necessitates compensation. Incitement, in itself, does not obligate compensation. If both an instigator and a direct actor are involved, then compensation is solely binding upon the direct actor.