Q.How to prune a smoke bush
I have a very large…10 ft. smoke bush with small leaves and flowers on just one side. Idon’t want to cut it all the way to the ground to rejuvenate. I love the shape and size. Can I remove just a third of the stems/trunks to help it along? How longwill it take to fill in again?

While you can't prune without losing size, your bush will look so much better, and flower so much more, that you won't mind. Something many people don't understand is that you can cut a plant almost anywhere, and it won't damage the plant. Also, all you need to do is stand back and look at your plant, and decide how you want it to look, and cut off everything that doesn't fit within that look. You only need to cut what you are comfortable with. This article discusses some more of the fine points: https://www.gardeningknowhow.com/ornamental/trees/smoke-tree/pruning-smoke-trees.htm