When working on your reel, place any small parts like screws from the handle locking plate into a plastic container which contains a small amount of car engine oil.  I use the plastic caps off spray cans.

By placing these fiddly bits in the oil, it will clean and protect them.

Even more important, if you happened to knock the tray or work surface you are using, you're not going to lose a small part which could easily get lost.