It's one of those things that should've bee addressed with some kind of ingame janitorial room to let you try them.

Cleaning up the place also seems to have no ingame function, not even a VO telling you you're doing your janitorial duty. It just seems to give some achievement and nothing else.

I feel the game did fine tutorializing it without it spelling it out for you. Like how Joel X mentioned, if you observe the pig/boar mutants, they go from bloodstain to bloodstain. Likewise, in Security, you're warned the Steve 02 cleaning bots do NOT like things being messy. That said I never tested how much mess pisses off the cleaning bots since I was cleaning up for fun anyway — 1920 bloodstains cleaned by the end of the game according to my statistics (plus I cleaned up oil and acid, too. Shame you can't clean up puddles). That's just how I play.

Some things are just fun to figure out on your own, and feel rewarding exactly because the game doesn't directly tell you. For example, did you know if you upgrade the Flare Gun and shoot a depleted battery with an electric shot, it charges it? Just look out for the tier 3 upgrade that also explodes the shot, because it takes the battery with it if you're too slow.

As for the spray uses, yeah, that's pretty much all of it. Only thing to note there is another fully upgraded gun, the Steve 02 turret that can ignite them.