i need to get to bed but REAL QUICK:
if you search "twitter" on this forum (the lil magnifying glass up in the top right) you should be able to find a few different threads of folks sharing their twitter handles if you're lookin for folks to follow! (you might also find some useful advice in a few other threads on using twitter effectively!)
My advice is always, follow folks who are doing the kind of thing you want to do -- whether their personality is really encouraging and inspiring ( I always recommend evegwood, valeriehalla, and if you dont mind a bunch of shirtless fellas on your TL jendrawscomics for their SHEER ENTHUSIASM AND EXCITEMENT ABOUT COMICS) or if they're making the kind of content you make -- and then (1) you can kind of pick up by example what sorts of tweets work and what sorts of tweets are entertaining etc, you can pick up some tweeting etiquette this way if you watch how other people use twitter, how often they bump or retweet or quote-tweet their own posts and you can see how it affects you and how many tweets feel like too many or just enough; and (2) it puts topics on your timeline. If everyone you follow is talking about when they first started drawing or how to write effective villains or how they handle conventions or whatever, and you have some thoughts on those topics that you don't mind sharing publicly, then tweeting feels more like you're adding your thoughts to an existing conversation, reacting to it (even when you're not directly replying to anyone) instead of having to come up with things to say all by yourself.
you can also just post like....sketches on twitter if you don't like coming up with things to say. Having a mostly art twitter is something some folks absolutely do!
In general I think the ancient internet adage of "Lurk Moar" is a good policy for learning any social media.
As far as hashtags go, I know #webcomicchat is still going -- if you follow the @webcomicchat account, there's a couple of hours on the weekend where it runs a live discussion of a comics-related topic, which can be a fun way to find other creators. I'm actually not sure about others! But this is something else that following similar creators is good for -- you can be alerted to relevant hashtags when others start tweeting about them!
anyway im shazzbaa on twitter so if ur lookin to follow some comic artists feel free!! or feel free to not follow me and follow other people who are closer to your jam!! and honestly feel free to ask any questions you have!!!