MusicTechHelpGuy demonstrates two ways to build a delay throw on a vocal, using Logic Pro's tape delay to bring the effect in only on specific words or phrases.
The first method automates the wet parameter directly on the plugin, keeping the dry signal at 100% and riding the wet knob up for a single word, then pulling it back down before the next line.
His preferred method moves the delay to its own aux track instead. Set the aux dry to zero and wet to 100%, then automate the aux track's volume fader to bring the delay in and out exactly where you want it.
The aux approach gives more flexible, musical control since you're automating one simple volume fader instead of hunting for a specific plugin parameter each time.