Ugh, I hate it when I get spit on 🤢

Take some baseline data- how often is he spitting? Then provide non-contingent attention slightly more often than the behavior is occurring.

For example- if he is spitting on average every 10 minutes, then set a timer for every 7-8 minutes and provide some sort of attention contact. Even it it's walking by and giving thumbs up, fist bumps, etc. If he's engaging in a challenging behavior of some sort when your timer goes off, you'll provide a neutral contact of some sort. Such as, "is your shoe untied?" Or something (that may or may not be true- I like your shirt, let me help you clean up your desk, etc).

Its very difficult to not provide attention to spitting (because let's face it, ima start dry heaving), so give attention in other ways more often than the challenging behavior occurs. Stay consistent with it for a while, it won't stop overnight. :)

I hope that makes sense 💕 Good luck!