Ask HN: How to hire engineers to refactor legacy codebase

Our teams responsible for shipping highly code in a waterfall like schedule that integrates with tons of other libraries and is very perf, cpu and memory critical. There have been many folks that have worked on this for the last decade or so. What types of engineers would be interested in working in such an area? How would one motivate them? How would you go about hiring high quality talent to do the same? What level of experience should we look for? How do avoid fatal pitfalls?