Markdowns

Using GP10SP5 We sell on the internet. We have some products not moving and we want to mark them down, the whole remaining inventory for those items.  What is the best way?
Do I need to create a new price level? For example the original was set as "Retail" so do I need to create a "Disc1" level and if still not selling Disc2, etc.
Or do I use the Markdown field?
thanks!