If you want to bulk update the quickest way to do this is via CSV. This can be for useful when you need to mass change weights, commodity codes prices etc.
1 - Export your current product data
Go to Products -> Overview
Select the product you want to export. - Note Change the number to display if you want more than 10.
Bulk Actions -> Export To CSV
That will generate a CSV file:
2 - Make any changes you need to the product data.
Once done save the file.
3 - Upload the Product Data back into the system
Products -> Extras -> Upload Products
Select the file to upload.
4 - The results of the upload will then be displayed: