Aylwen Gardiner-Garden

My elders are Sambucus nigra, and in our drought they need watering to survive. I've got berries drying/dying in their bunches on the trees and some trees all the leaves have dropped off and I need to do overnight remedial watering to see if I can get some new growth. I was wondering though if its best to prune back when harvesting the fruit in summer or in winter when dormant? And for those that prune, how much do you cut back?
As for their medicinal content - I normally use the cordial with hot water in winter but wondered if some elderberry wine I made a few years ago would have similar medicinal qualities?

Its summer in my Australian (Canberra) garden and we're in drought and already this January we've had hail the size of golf balls, heatwaves and bushfires. Somehow I managed to get enough berries off my elders to make cordial but the trees have been suffering in the heat.
I was wondering what pruning methods and when others employ when growing elderberries in hot dry conditions, and winters that go no lower than 14F (-10C) without snow.