Because I have some online watches for names of Energion Publications authors, I found the post In Search of Sinless Perfection, which quotes Alden Thompson. This comes from a Seventh-day Adventist background, but I must mention that I have been surprised by how much from my own SDA background simply translates into Methodism. One may easily underestimate the impact of the fact that Ellen White, early SDA leader viewed as having the prophetic gift, was a Methodist before she joined the Adventist movement.
In any case, Ellen White quotes aside, Loren Seibold, author of the article gives a number of the reasons I have for questioning the idea of sinless perfection. Certainly the Wesleyan doctrine as actually taught by Wesley (try here for more, though you may find the account less plain than you imagined) seems less problematic than its various descendants.
I love the introductory story, which ends:
Then the perfect man hung up on me.
Perhaps not the ending one imagined for a conversation with a perfect man!
I too am a believer in sanctification. Where I must get off this particular train, however, is where one gets a personal knowledge that one is perfect. I just can’t see how that would work.