John Wesley, Anglican clergyman and movement founder and ultimately founder of the Methodist traditions, did teach that perfection was possible. He is the first person, I believe, to preach such a thing. It was controversial. However, we have his published writings on the topic. Indeed, we have a a series of writing, so we can find out what he had to say, be inspired and be corrected by it.
He defined perfection as being without sin. People thought a great deal more about sin then than we did now. So “sinless perfection” issued later in the holiness movement. Wesley outlined in what way we could expect to be perfect. He very much had urged against judgmentalness. His method seemed to be devotion. He was not preaching legalism! Quite the reverse!
The Latter Rain and the Same Fife Move of God were informed from the holiness movement, but not much from Wesley. Therefore, in order to re-preach sonship, faithfully, fully, Biblicaly, and within orthodoxy, we should start with what John Wesley had to say.