A way to show form is submitting or stop double click submissions

Hi All, I have two forms that take between 3-90seconds from the point submit is pressed to the point confirmation is displayed, is there a way I can easily show user that the first submit click is working to avoid double entries.

I was thinking something like a status indicator showing submission progress. or get the confirmation instantly and have the rest done in background

these forms use a mixture of gravidypdf or gform_after_submission to send to MySQL which adds to the submissions time

Any ideas would be appreciated