How to prune bottle brush?

Usually after flowering is the best time,it encourages new growth and helps to keep shrub tidy

I have been growing one of these for twelve years. The only attention I have given it is to cut out any shoots heading too far out from the bush right back to where they meet another branch. I haven't fed or watered it but it seems quite happy. The first winter is the critical time; once it has got through that OK, it seems to cope with anything the British weather throws at it