Google will set you free...

site:bikeforums.net snotrockets

You will learn more than you might want to know.

This is an excellent skill to learn. It is handy when you are out in cold weather with no tissue and wearing gloves.

Done properly, it is actually pretty clean.

Maybe it's just me, but I find the sound, similar to a large spitwad striking a forehead, very gratifying.