Toilet stalls are a great starting point for immediate practice for messaging. Something as easy as a sharpie, or more advanced like stickers works great – for revolutionary quotes, advertising radical student orgs, critiquing, some new event…
Graffiti is only recommended in some area outside
the premises, where you know there's no surveillance, perhaps on the road or electric boxes towards the nearest public transit (and make it in the middle of the night or something, but be aware that security could still be on watch over the general area (paid for by the uni) - so act with due caution if you'd do this). See the Situationist's theory of 'psychogeography' for more of this, but modify the context to the present one of abundant surveillance. I'd recommend you take the first month of casual strolling with a cap/sunglasses to self-surveil the surveillance, take a google-maps screenshot and mark out where the surveillance is most intense and where it radically decreases, taking into account windows and especially corners as well. A stencil graffiti of a communist quotation or a visible hammer and sickle makes the intellectual climate for students more liberating as they know there isn't all just 'apolitical' libs all over the place; it functions as a giant 'OK' sign those quiet. All this while never making your political views incriminatorily obvious as a 'Subversive Agitator' to potentially get you kicked out of the uni; it should all be carried out relatively secret until actions gets sprung up spontaneously, go ahead and support them, but still with some distance, acting like you just heard about it like everybody else, so as to not get targeted as 'the Leader'. Use a VPN for your devices, if things kick off don't use things like Facebook as they collaborate with authorities, but instead be the pseudonymous admin of a Riot.IM group or something and post that also in the stalls (this is after
things have actually started rolling).
Bam, maybe you've just radicalized several hundreds of students for the foreseeable future, who knows.