if your custom blog application will be part of Sitefinity, you should use Blogs API (e.g. the standard Blogs module is using Blogs API). You can reuse some controls of the admin area, but since we have not tried to do that before, we cannot say if you are going to experience any problems with that.
We have a video on our site which I think will give you a good idea on how to start working with Sitefinity Blogs API:
I hope you'll find this information helpful. Let us know if there is anything else we can do for you.
the Telerik team
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