fear of rejection technique, will it work?

[Mojon]

ok im average when talking to people always conservative in my body language and words trying not to speak whats in my mind. No GF in years no fun for many years. I have an idea that consists of, isntead of looking for aproval, seek for rejection , to overcome my unconfidence by saying things or acting in a way that people may reject me for sure. Example: singing while walkig in the mall, asking a random girl for her number without previous conversation