After 20 years of trimming 15 foot high privet bushes, I finally did this...hired someone to do it for me. Worked like a charm. ;-)
My next hedge trimming job will involve removing about five dozen maple saplings that are growing up inside and through my hedges.
Electric clippers are wholly unsuited to this. Calls for an old-school manual approach using wire cutters.
I have to lay waste to all the little maple trees every year. Sorry, Canada!