Don't get disheartened! I smoked for 40 years before I entered the wonder world of vaping. Some pointers:
Don't try to emulate cigarettes, you can't! Instead go with something with a bit of a tobacco undertone, like VCT
Find an eliquid they love, mine was a mint, tasted like gum and I could vape it all day.
Make sure the process isn't too complicated. Our old hands can't manipulate all those tiny pieces.
Progress, not perfection...... I went from 3 to 4 packs a day down to 5 cigs a day. I know, I know, why not just give up those 5? I am not sure why, but I can't. And it took me 2 years to get down to those 5.
One last thing.... if this is something that a smoker doesn't want to do, you can spend a lot of time and money and get absolutely no where. Involve them in the process of selecting flavors, maybe try to unravel their taste buds.... if they are truly interested, than you will hit on a satisfying substitution, and then give it some time.