Store Commander allows you to setup sales on products very quickly wether you use the interface or the CSV import tool.
Using the interface
The quickest way to create a discount is to use the Specific Prices panel accessible from the Properties column.
Select a product and open the Specific Prices panel
If multiple products will benefit from the same discount, then select them all and refresh the Specific Prices panel
Then click on the icon
A line will be created for the product IDs selected
Enter the discount amount or percentage in the Reduction column - use % for a percentage
Select the start and end dates (select the minute before the day in the calendar)
Finally, refresh the panel
This is it, the discount is now setup on all the products you selected.
Check the procedure in this video
Note that scheduled discount, non active, will not be displayed in the Discount view. Only active ones will be. Refer to this article for more detailed information.
The last thing to do will be to enable the 'on sale' logo on discounted products (during sales periods).
Because this field is not linked to the Specific Prices nor Discounts, it cannot be enabled automatically. So you will need to do so manually in the interface.
The quickest way is to display all your discounts in the Specific Prices interface (accessible from Catalog menu) and use the copy/paste option.
First modify the 'on sale' to Yes on the first discount price
Right click on the 'yes' you have just chosen and select Copy
Then select all the other discounted prices, or use the mass selection icon
Right click again in the same column and select Paste
Here you go, the 'On sale' logo is now enabled.
Using the CSV import
If you have hundreds of products you need to setup a discount onto, the CSV import tool will be more appropriate.
You can refer to the article below for detailed instructions.