I just take a grug brain approach. I do touch CLAUDE.md and then just explain how the code/files/project spec work, like I'm writing a slack message or email to a really smart colleague, and then let it rip, always using biggest model with thinking on. If something consistently goes wrong I add more to CLAUDE.md or even better, have Claude Code just update CLAUDE.md itself with the new issue explained. I'm probably 3 months behind what you could get with absolute SOTA practices but it still works so well that I'm amazed and amused on a daily, if not hourly, basis.