Thanks for the reply! I haven't really checked the Webtoons app, always accessing their homepage when I read. ;A;
I agree with Facebook and Twitter. Tumblr is an easy way to self-promote, too especially if you have a lot of followers. It spreads the info through reblogging which is neat.
As for SmackJeeves, compared to how it was a few years back I noticed it has become a lot more quiet these days. And Tapastic seems to attract more readers especially when you update like a page every day or at least every other day.
For now my best bet would be Tapastic since we got the best response here so far. (´・ω・｀)
And yes, more exposure---the better. We have people on other sites that don't use another.