well as we know genjutsu is the form of techniques that are related with fooling the opponents senses, by this it can apply the means of using the targets senses i.e casting a genjutsu with the finger is corresponding with the targets sense of sight, which casts the illusion, others can be hearing like toad duet illusion does, well the similarities in these are use of chakra probably, if u manage to place a seal over the targets that intercepts the target from using any form of technique that corresponds with your senses it'll just work right? so with your so far knowledge of seals make 1 over that'll stop me from casting a genjutsu over you