It's like hammering on and pulling off. You press on the string on whichever fret and then pull off.
define flick.
Dissonance is Bliss

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Member #4 of the Carvin Club
This whole time I've been hammering on with my tapping finger but I've noticed my friend tapping on an acoustic guitar by sort of "flicking" the string with his tapping finger and it sounded much louder than mine.
I do most of the time especially on my acoustic so I can hear it better., I don't really use tapping though.
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Squier SQ MB-5 5-String Bass
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Yeah, to get a louder sound that wont differentiate from picking, you do have to kind of forcefully roll your finger off the side of the string. Also to keep the other strings from ringing out plam mute the lower strings with your picking/tapping hand and mute the others with your fretting finger. It can be kind of tricky to get down, but once you can properly do it, it will definitley improve your confidence in your playing.
I find flicking to be much more effective. Try and learn it. It was never even something I thought about, it just kind of happened by itself.