dont treat a conifer like a ficus. foliage for junipers is their life support, you gotta creep your prunings gradually to reach your goal on these trees.
Jelle on point with the tips... 1-2 year window when you chop some off, and make sure there's plenty of foliage left to keep the tree alive.
I'm a novice, but with junipers it's all about pad creation/ramification, going easy on the hard prunings and root pruning, and timeframes are a lot longer because they dont recover in half a season like a ficus or bougainvillea.....