How to disvow effectively?

Hi all

I am writing this as a question as I am not quite sure I know the best way.

Hope someone here can help?

I heard that with disvowing (not sue that's a word) you can get rid of all the not so great backlinks. It sounds great for a clean up it seems to involve sending messages to Google to explain you do not want any connection to the link.

I could potentially get rid of 40K rubishy backlinks from my domain how fantastic :)

Here's my worry if I send that many links…

How to disvow effectively?