[snip]
I used to use a hedge cutter on my 200ft beech hedge, but have since found
that using secateurs I can 'prune' branches to up or sideways pointing
buds,
thus thickening up the hedge.

BTW It's best to leave pruning until the hedge is dormant, although I find
that pruning in the depths of winter, removes a lot of the brown leaves,
so
I tend to leave until spring.

I've also read that when you want to reduce the height of a hedge, you cut
back to about one foot lower that you want, which allows the bush to grow
naturally up to your preferred height rather than just looking hacked off.
This presumably applies more to a "thorough overhaul" than a regular trim!
I imagine similar applies to cutting a hedge back too.

Paul DS.