I, too, have never heard the phrase "blow away the cobwebs." This could be because I am American, and the idiom dictionary specifies that it is a British and Australian phrase.
In American English, the phrase "to sweep/ clear away the cobwebs" is not used the same as the British "blow away the cobwebs" phrase.
We use it as a metaphor. When a room goes untouched for many years, spiders make cobwebs - the thick white webs not the pretty ones you typically find in nature sparkling with dew. When we want to use the room again, we have to sweep the cobwebs and clean the room first.
The same goes for other things untouched.
Marie has not played the piano in 10 years. When she sat down to play yesterday, she had to clear out the cobwebs before she could play a song.
In this example, Marie has not played piano in a long time so she has forgotten a lot. Before she could play the song, she had to think for a minute and remember how to play.
In the blog's case: "It’s time to open the windows, clear out the cobwebs, and sweep away whatever has been blocking your dreams!"
Sometimes, our goals/dreams are never achieved because we concentrate on work, family, rent, etc. We let our dreams collect cobwebs because we are not working toward them, and now the cobwebs need to be cleared away before we can achieve them. Colette Baron-Reid is saying that now is the time to overcome obstacles (the cobwebs) that prevent us from realizing our dreams.
I hope this helps. Let me know if you need more examples or clarification on anything!