It's to be expected that some of your blog posts will have a hook to whatever your selling. Every single post might be overdoing it slightly, but certainly some would be a good idea. Not just for sales, but also for SEO.
If one of your blog posts becomes very popular, as in it earns external links and social signals, it will become a strong page on your site. If you link your strong pages to your key landing pages, some of the SEO strength will pass through. Furthermore, your internal links can use a lot more exact match anchor text than external links, so feel free to link to those pages with the keywords you want to rank for. Again, don't use exact match every time, but you can use it much more often than with external links.
Hope this helps.