is it hard to obtain walk-in permits for 6 for 7/7 for Cottonwood lakes?
On all trails except the Whitney Main Trail, 60% of permits are reservable 6 months in advance, and 40% are held back for walk-in requests. Those 40% are made available at 11 AM, the day before the hike entry date. There should be a good number available.
For that trail head, JM39 on this doc
, there are 24 walk-ins available at that time. There just aren't 24 people who are going to take that risk, so your chances are VERY good.