If you want to echo or verb only certain words of a lead vocal, just duplicate the track, add the desired effects (making the echo or verb 100% wet) and chop out everything you don't want to process. This is - for me - the quickest way to process only specific words and syllables.
Here's how I'm doing it on my remix for the upcoming Winter Kills single "Hot As Hades":
Speaking of... I gotta get back to work.