How To: Fade-in words in a sentence, then fade-out trailing words as the fade-in progresses.

I want to fade-in words from left to right, like the effects pre-set, Slow Fade On, does. But, before the sentence ends, I want those first words to begin fading-out as the later words appear… and then they finally fade-out.

I can do this by creating three identical layers, and varying the opacity levels… but that seems clunky. Ideas?

“his life past him like a dream, and memory faded like smoke in air”