I have been told that blog commenting is an effective SEO technique.

Currently I have a sale page with 3 products. For example purposes I will call my category: vintage cars and my products v1, v2, v3.

Although I believe that I should use both my caterogy and products, so far I am always using my category keyword (vintage cars) as I have yet to find blogs which allow links in the comment box. I am slightly worried that the link building might not look natural to google.

As the weeks go by, how do you keep track of the blogs that you have already commented?

Any suggestion would be greatly appreciated.