Every Weblog II page now has "flush cache" buttons on the /edit page.

To see/use them, just go to your weblog and click the "Edit" button. (If you don't have an edit button, you didn't put it in your template. In that case, just add "/edit" to the end of your weblog's URL.)

You can either flush the entire cache with the button at the top of the page, or only the cache for a single day with the button at the top of each day's editor.