Yes most definitely prune them back and they will come back beautiful. My husband prunes ours with hedgers and it doesn't hurt them at all. It keeps them in a uniform shape.

wait until the forsythia blooms in your area (it is a large shrub with yellow flowers). It should be in the next few weeks (the ones here are late this year).

Double KO doesn't need anything special for pruning, hedge clippers would be fine. Use hand pruners to take out any dead or damaged canes.