Not as much of a solution as it is some tips. This is easier to do with someone who has an ultimate that is an AOE (Poseidon, Ratataskor, Scylla, etc) or ranged gods that put out a lot of damage (Artemis, Chiron, Apollo, etc). This can be unlocked on Fire Giant, Gold Fury, Bull Demon, and the bonus Siege Monster. This is the Siege Monster that sits in the middle of a map that either team can claim. Not the ones that are summoned after every 100 minion kills. Put wards on the objective/s (good tip in general for Smite). This one is kinda luck based. Just keep at it. Hope these tips help.