WordPress By Yoast: How to delete all existing title

Hi everyone,

I have a wordpress blog with over 450 posts. I want to force rewrite all my posts’ titles to use the template that I set up, which is %%title%% ? %%sitename%%.

It works great on new posts and existing posts where I have not filled in a specific title in the Yoast box in the post editor. However, over 400 of my posts have existing titles in the Yoast box which is just my post title and checking “force rewrite” isn’t overriding them.

I’ve found I can go into each post and manually delete my existing titles in the Yoast box for it to use my template, but over 400 times is just too time consuming. Any suggestions on how to force rewrite all my existing titles or how to delete all my existing titles to use the template?

I’m using latest version of WP and Yoast.
I’ve tried checking the box for force rewrite titles on and off
in Header.php I have the following title code
<title><?php wp_title(''); ?></title>

Thank you for your help in advance!