I believe you have very good idea about how beneficial it can be to have .EDU back link to your website and that also whenever you want and to which ever site you want.
You can easily find .EDU blog sites by using following keyword:
site:.edu inurl:blog "post a comment"
By using above keyword i have personally found hundreds of .EDU blog sites which have pagerank in between 3 to 8. You can easily post comments and generate backlink to you website.
I have personally found hundreds of such .EDU links and i easily get backlink to my website from these website whenever i want.
I would suggest commenting manually not using any software and before posting comment please read the contents of blog post or at-least get the idea of blog post contents and post respective comment so your comment will be approved.