This year I planted a Paulownia tomentosa in my euphemistically named 'tropical area'. It has grown well on a single stem and produced about half a dozen decently sized leaves. I know that to get the foliage rather than the tree you have to cut it back each year, but by how much and when?
The stem has several pronounced 'joints' along it before the main leaf stems so I'm guessing to cut back to one of them - or right to the ground?
I don't think there is any particular way to prune them back. It might be a good idea to post a photo. Sounds like you only have one stem with a few branches coming off the main stem? The description of your tree is of a very small specimen with few multi-stems near the base. I think that reducing the height down to a few feet should be fine. From what I have heard, they are quite fast growing, so should bounce back quite quickly. Do that in early spring.
The biggest foliage is achieved by cutting almost to the ground in spring and only allowing one stem to grow back. The more stems you allow, the smaller the foliage will be.