Getting the trim perfectly dialled in with an engine out takes time. Time I found I didn't have. Instead, I'd get the trim close to where I needed it, and just apply control pressure as necessary. That way, if i get distracted and inadvertently let up on the rudder pressure a bit, we didn't go flying off in some new direction. The change would be slow enough for me to come back and correct it while still maintaining standards.
Out of curiosity, what airplane are you flying that has auto trim?