If you have barcodes for your products, you can scan them to automatically update your overlays in real-time. Barcode scanning is not available on the Basic plan.
And then just scan your products during your live by placing your mouse cursor in this field in your Overlays tab:
Each scan automatically updates your overlay. Here's a short tutorial demo of the barcode scanning feature in action.
If you don't already have barcodes, you can use Shopify's “Retail Barcode Label” app to make them. It’s free and just does the basics. You can manually create barcodes in a few clicks to all products that don’t currently have barcodes. And you can print out barcodes as well.
You can use either the SKU or Barcode fields. SoldLive looks at both when you scan a barcode in the Overlays tab.
If you don't have a barcode scanner and need a recommendation, this one is only $35 and works well: https://amzn.to/3mNBMcF