I do nothing. I'm not active/motivated to post on social media, I only share my posts on twitter after i upload an episode, but...i only got 4 followers there.
The only place my webcomic do good without me having to promote is Line Webtoon. Every other site i post my stuff just go unnoticed, so i always just end thinking my comic is not good enough outside of Webtoon's audience.
I think the other places are more elitist, or the art there is way out of my league (like top artist on instagram or deviantart, yeah...i'm not at that league).