Self promotion just takes as much effort as doing art itself. That's what I realized recently. And would really take a long time to gain an audience. So patience is a must. Even though you're shouting to the void, just keep shouting, someone will eventually hear you. Also, you really need to engage in communities tho I still find it difficult sometimes since I'm not exactly those sociable types.
I personally feel that I'm holding back in Self-promotion because I don't want people to think I'm too spammy but I think I should be a little aggresive when it comes to promoting my webcomic.
I won't force you if you don't like using twitter. I didn't understand how to use twitter not long ago until I tried it myself and now I use it more frequently than any other social media. I love how I can easily communicate with fellow creators there. I love #webcomicchat although I can't partcipate in the European ones since it's sleeping time in our place.