I assume this is the same guy who told you not to use cool power fuel. Sounds like he has been flying 2 or 3 months and is already an expert.

You really don't need a tachometer. Tune the high end for peak rpm, idle down and tune the low end until it trasitions fairly smoothly and won't die at idle, run it back up and richen the high end
until you hear the rpm start to drop (200-300 rpm). Stop right there and leave it alone.

As the engine continues to break itself in the idle will become more and more reliable. Trying the tune the low end perfectly when the engine isn't fully broken in is a waste of time.

Regards,
doubledee