Is it possible to auto populate existing records with new information?

Is it possible to auto populate existing records with new information?

Our Creator database consists of a main form with several sub forms linked. We use the main form to collect demographics and the sub forms to collect specific information about the product purchased. We would like to be able to pull reports that include information from the main form and a sub form. I believe the easiest method would be to add the demographic information to the sub forms (I have worked out the code to auto populate this information moving forward) but I do not want to have to go back through each of our records to update this information. Is there some sort of script that we can add or bulk edit function that would allow us to easily update our form information?

Assistance is greatly appreciated!