Trees, Shrubs and Conifers: Care of mature cedar hedge, 1 by Erynne

Erynne wrote:
Hello!
Hoping someone could help here before I let DH have his way with the hedge trimmers this coming weekend. We moved to a property last year that has 20ft tall cedar hedging on a good portion of the perimeter. The cedars appear to be in good health and are teeming with wildlife. I would like to know how we should go about pruning these cedars considering that they haven't been pruned in nearly a decade with the exception of one portion being cut away by the electric company (growth too close to hydro lines) according to a neighbour. The growth is definitely unruly in many places with thicker branches jutting out.
I live in a hamlet called Cedar Valley in Ontario zone 5a ....so when and how to tackle this would be most helpful. I guess it wouldn't hurt to know the proper name of these cedars as well.
Here are some pics to give you an idea.

Many thanks,
Erynne