The best and only way you should cum doing it alone is cumming in your forsekin, here’s why:

* It’s ecological because you don’t have to use paper
* you grab your forsekin and the cum won’t come out until you stop squeezing with your hand
* you can control how you throw away the cum (in the toilet, bathroom or whatever)
* you don’t have to control the stream of cum because your foreskin is containing it

And also bonus point because you know how much you cummed and can compare it with the last time you wanked