Have you ever experienced "vaper's tongue"? Leo knows all about it... It's caused by some sort of film build up from the PG, VG & flavoring.
If you want your mouth to feel amazingly clean, as any former smoker would want, you need to use a tongue scraper daily (It should go without saying that flossing helps too, but the tongue scraper just brings it to another level.) Finish with a little mouthwash, and your mouth will never feel so clean.
I use this brand, because it's the best and you get to subscribe to receive a new one each month for just $1 (+$2 S+H)