Some mowers handle wet grass better than others.Run a test with yours and see at what point of dryiness it doesn't stick to the deck.That should be your starting point. Start on the lawns that are open and airie with early sun, they should start to dry first.
I know this sounds crazy and TRY not to laugh at me too hard guys, but try this it works! After you clean your deck out next time,- it usually cleans better right after we've cut wet messy stuff.(That's not to say you have to wait until you encounter such a thing) But anyway, as soon as you clean it out good, go in and steal your wife's (or girlfriend's) can of PAM cooking pan spray. This does WONDERS in preventing under deck buildup and makes the next cleang ALOT easier. Just remember, like the dishwashing liquid, to put it back.