To improve speed and quality in iOS builds, developers can use Bitrise's fan out feature, which allows running tests in parallel on multiple virtual machines. This setup can significantly reduce build times, but may also increase stability issues if not managed correctly. The article describes how to implement this feature using Bitrise workflows, including triggering fan out builds from a primary workflow, collecting test results from each fan out workflow, and generating a single test report. By splitting tests into chunks and running them in parallel, developers can take advantage of multiple virtual machines to speed up their build times, making it an attractive option for large-scale testing and automation.