How to trigger/run/execute scheduled task manually?
This is how i do it, I use flags module, i create a user flag for each  "run manualy my special rule" assigning flag/unflag access only to admin user and i display link on user profile page, flagging or unflagging myself to trigger my special rule, then, most of the time i use views rules module to load content, products, orders or users and perform any kind of stuff with it.