Well I gave a basic description of one effective process for using expoy. If you were to use something like a silicone caulk, you'd need something to hold the resistor and reed switch after soldering. You could use a small vise or a thrid-hand, even a pair of clothespins, anything that will allow you to apply the caulk around both components and allow it to cure for 12 to 24 hours without touching anything. If you are using hot glue a vise or third-hand would also help, but it would take less time for the glue to cool than silicone to cure.
Whatever you encapsulate the parts in make sure it yields a water-tight seal that can also absorb some physical shocks and is electrically non-conductive.
By the way it is possible to buy reed switches that are already encapsulated, some even in packages with mounting slots.