I agree with this advice about walk-ups! Never been turned away when I got to the visitor center on a weekday; only missed getting a walk-up once on a Saturday (and even then, I ended up returning later and getting one for Sunday). Also, I've found in the past that the best times to check recreation.gov for newly available permits are a few minutes after 7am, 11am, and 2pm. They do NOT claim to post available permits on any time schedule, so take that with a grain of salt.
