I do put my hands in a bit -- feeding shrimp/coral, brushing off algae off the rocks etc.
I always make sure I've washed my hands fairly recently before doing so. If I handle any cleaning sprays/wipes/liquids or whatever, I make sure not to put my hands in or near the tank for the rest of the day just to be sure.
I don't keep any aerosols in the house because I've always been paranoid having anything near the tank.
The only thing I use on the tank (to clean the glass, or any salt creep) is a spray bottle with water and some vinegar in it.
As far as pests, nothing that I've ever noticed..... I try to take random peeks at night after the lights have been off for a couple of hours. I've never noticed anything on corals or any kind of bite marks or anything. I've never seen any type of flatworm in the tank, the only things that I can think of that I've seen at night would be micro brittle stars, bristle worms, and I quite a bit of chitons in there, but I don't think they would be bothering anything?