Can I take a pre-exisiting list and subscribe them to our main newsletter list?

Hello!

I am looking at sending an email campaign with an intro to our company (a marketing email), but they’re taking part in an upcoming trade program/contest and the program owners have given us this list of emails to send an email to.

They DO accept marketing, but I want to send them this initial email first, and would like them to join our main newsletter list at a later time (after this email has gone out). However, anytime a contact is added to our newsletter list, they go into our welcome series. I do not want them to receive our regular welcome series email. I have created a separate list that i will send this campaign from.

I know I can add a customized profile property tag when uploading this CSV ie. “Brand Tag” and can manually upload this list again to our main newsletter list and add a flow filter to the Welcome Series Flow of “Customized Profile Property Tag” does not equal “Brand Tag”.

• I guess my question is, would the above be the correct way to do it?
• Or is there a way to move this list to the main newsletter list in an easier way (instead of re-uploading them)?
• OR do i just upload to our main newsletter list at the start and ensure the flow filter is turned on with the “customized profile property tag” does not equal “Brand Tag”.

Thanks in advance!