Hello Achao,
Welcome to ECF!
I think the most important 2 things are to make sure your father has a good head (the top of the e-cigarette) and good e-liquid. What was he using for equipment? The small ones that look like a cigarette are not very good and that may be the problem.
If he feels uncomfortable using the e-cigarette in front of his friends you can tell him that the e-cigarette was invented by a doctor in China, and that China makes almost all of the e-cigarette gear that is sold today. I buy almost all my gear, and many liquids from China.
Also tell him that he doesn't have to quit right away, he can use the e-cigarette to help him quit slowly. If he smokes less because he uses an e-cigarette, that is still a good thing.
Ask him what he didn't like about the e-cigarette. An e-cigarette is not exactly like smoking. But many people like it better than smoking. Make sure he tries some e-cigarettes that do NOT taste like tobacco, but taste like fruits or other things he likes to eat. I have cinnamon-roll, peach, coconut, and even litchi flavors that I like.
If you can tell us what type of e-cigarette he used we could give you a recommendation for something that might work better.
Good luck!