Attaching multiple files to a SharePoint List

Hello,
I have a client list in SharePoint 2013 that and attachments are added to each item. Many times one client has multiple attachments associated with their name. Currently I click on each item, go to Attach File, and I can only add one file at a time. This can be very time consuming and can cause errors if I add the same file twice without noticing. I've searched for solutions online and they all point to running a script which I've tried but it still doesn't quite work. Also, each solution online has a different script, with some indicating there should be a loopback added so you can get this option to work every time you click on an item. Essentially I'd like to highlight the attachments associated with the client and attach at once. Is there an easier or even specific way to get this accomplished? Please help.

Thanks!