It really depends on the situation. I really don't know if I'm a good liar for myself because the worst thing that can happen to you is getting away with something. If you have any decency, it doesn't feel like getting away with it. If anything, now that you got away with it, you have to live with it. But now that time has passed since the transgression, coming clean just isn't the same thing. In fact, coming clean once you "got away with it" now has zero nobility to it. And it doesn't matter how small the transgression was. Heck, I can recall hiding from a friend at age 7 because I didn't want to play with them that day. They were quite annoying and I just wanted a break from them, but having my mom tell them I wasn't home when I was there felt wrong once it was in motion. And the way things affect people, that person could be on a couch today talking about how he lost his confidence that day. And if I ran into them today, would it be better to keep up the ruse because maybe the truth would be more painful? So that really wouldn't make me a "good" liar, now would it?
But there is also the difference between lying for your benefit v. for the benefit of others. Growing up with people that had their own issues, I'd find myself lying or "covering" for them. It didn't have to be a lie. It could just be acting obtuse or lie by omission.
And finally, you have the flip side. Being a bad truth teller. There is somebody in my life that is borderline "losing it". See. I lied right there by adding the word "borderline". A built-in protection method for people I care about. Any way, they have become seriously paranoid now that they are in that horrible stage of life between sick and death. And this person constantly accuses me of stealing their stuff or sabotaging them. Really stupid things like they misplace a phone and are positive you either a) stole it or b) hiding it to screw with them. This person thinks they are Perry Mason or Sherlock Holmes. They can "read me like a book" and will bring up things from when I was 9 or 18 or 23 that they think I did, but did not, as evidence I've lied before and therefore am lying again. So when they have some medical episode with their meds and decide I've stolen their phone (even though they just left it in the bathroom), they go berserk. They will confront me and say "did you steal this? I can tell when you are lying." Now I know they are just in a "lost it" stage and I'm innocent. But I also know they are going to find the tell that isn't there. So I've tried monotone "No" and nice "No, but where did you have it last so I can help find it" to annoyed "No. You know I didn't take the phone" to silence - refusing to answer. They will find the tell that isn't there no matter how I tell the truth. And now it has affected me with others where even telling the truth feels unnatural.
The only way to be a good liar is to not give an F about the person you are lying to. Now I guess with a good liar, you can do that for everybody, which isn't really something to brag about. But on the other end, I guess if you had a boss that asked people to work Saturday, the ones that lied about commitments got out of it, whereas you were truthful and got stuck (for example); you might eventually not have a problem with a convincing lie about some family commitment that doesn't exist.
The reality is that it isn't hard to be a good liar. It is hard dealing with what comes after.