Have you tried building out your smart list with filters such as "filled out form" (your LP form used) and adding a constraint for the webpage the form lives on? This should pull in everything for you. You can even add in time periods if need be.
Note, this willl pull in EVERY form submission on that page with that form. If you direct other traffic other than your Google Adwords, this will be there as well.
From there you can use a flow to push to your campaign with batches or you can set up a trigger campaign to auto push these leads "if" appropriate.