What I did, when I was transitioning, was I told myself I could have a cig whenever I wanted one . .. but with one condition:
I had to have a quick vape session first, and then see if I still needed that smoke right away, or if it could wait a while.
For me in particular, that worked really well. I wasn't always satisfied; but I almost never ended up having that cig.
Don't remember how long it took (til I wasn't smoking at all); but it was like, IDK, 5 days? . .. a week? Felt pretty quick at the time.
Also, I got kind of lucky (didn't feel that way at the time). A month or two into it, I had equipment failure, and reverted to smoking for a few days while the internet morphed into a mailman. That was when I learned about back-ups. But, smoking for those few days made it really clear to me that I would never again find pleasure in it. So, I never miss it, cause I know I don't like it any more.