Wiring and bending after the growth has slowed. Branches sometimes die after bending while the sap is flowing strongly. I would think it is late enough in the season to bend juniper safely by now.
No problem pruning at any time of year. Plants have adapted to being eaten and broken by storms all through the year so they can regrow after pruning any time.
Some cuttings taken now may root before winter but a lot will not root until spring. Juniper cuttings can take up to 18 months to root.
I've been trialing wiring and bending tender long runners on shimpaku then layering them off afterwards. That way if the wiring kills them (and it sometimes does) I haven't lost a plant or wasted the time getting cuttings to root. I can get much tighter bends on thinner, softer shoots than on woodier stems.
It is almost spring down here and I removed a couple of these layers today because the parent tree was getting top heavy.
Shimpaku with 2 layers
layer #1 has a single root but that's enough to keep it alive while more grow.
Layer #2 has 2 stronger roots. Removing it from the parent now will make it concentrate on more roots quick.
The parent tree after removing the layers and shortening the sacrifice branches. Well over 1/2 of the foliage has been removed today and from experience I expect it to grow well now.
I'll be working on pushing foliage back and getting dense pads on the branches this summer and maybe some initial work on shari on the trunk.