Wesley is the originator of the Holiness movement ( entire santification)
The "method " was developed and practiced by Wesley and a Calvinist Whitefield (toplady a benefactor I believe)
The split between the two was when Wesley began to teach an Arminian doctrine with the holiness message added on (I believe influenced by the Morvavians)
Well, traditional Methodists differ from the Holiness movement in one primary way, with several others being direct corollaries of this main point: Methodists believe that the baptism in the Spirit occurs at salvation and is the means by which we are born again; Holiness folk believe that the baptism in the Spirit is something that happens later, and is synonymous with entire sanctification.
As to Wesley being the author of sinless perfection, no. If you want to define sin as strictly as the Westminster Catechism does ("Sin is the want of conformity to God's laws"), we have NEVER believed that anyone could be sinless. If you define sin as more a matter of motivation, then in that definition, it would be possible to be "sinless." The way I've seen it referred to best is this: we believe in a perfection that treads a line between "sinful" and "sinless" perfection, while being neither--it is instead, perfection in love. Purity of heart rather than clarity of head or absolute perfection of life.