Actually, the routine for an engine failure, how I learned it, was to trim two notches up (in a PA-28-161). That gave you roughly best glide speed (assuming trimmed for normal cruise speed), leaving you time to deal with other issues without looking at the ASI too much. Fine tuning the trim/speed was done after the other checks.
Unless you were very low of course (EFATO for instance). In that case don't worry about anything except finding a landing spot and setting up the approach.