"sinless perfection" is a misnomer that has been applied to the doctrine of entire sanctification as a straw man that is easily toppled by 1 John 1:8.
However, the doctrine of entire sanctification does not purport that a man can be made "sinless" so that "he can say that he has no sin" and the truth be in him;
Rather, entire sanctification teaches that the element of sin is rendered dead (Romans 6:6, Galatians 5:24, Romans 7:8) so that it no longer has any say over our behaviour (Romans 6:14).
For, we are not obligated to obey the flesh (Romans 8:12 (kjv, NLT))....
And, therefore, it is possible to walk consistently, not after the flesh but after the Spirit (Romans 8:4), for an extended period of time; even for the rest of your life (Luke 1:74-75).