There are two ways: Attack the battle
Knowing when to plot Slickshot and when to hard cast it will separate the best mono-red players from the rest
Equipping it to a flying Thopter is an easy way to get around blockers, especially since it protects from white (i.e., most flying creatures)
The trigger event doesn't have to specifically refer to "creatures." In these cases, the trigger event may also refer to something being "put into a graveyard from the battlefield." For example, if the equipped creature or an emblem you own has an ability that triggers "whenever an artifact is put into a graveyard from the battlefield," that ability would trigger twice if an artifact creature died
Obviously, the card has diminishing returns, but its also, at times, been a victim of its own success, pushing players to play more threes than they otherwise would for instance
That's a lot of mana for a rather meh effect, but if you can recur it you can get the effect multiple times