Well... It's more of a luck factor if you ask me, considering that many people, everyday at every hour work on their series and share their process on social media, as well for those that are fans of already existing series and just repost images of their favorite panels/characters.
So, like, anyone can use the hashtag without being a creator and most of the time people bury each other with the constant use of said hashtags. Not to mention how frequently some post on their socials, be it work in progress or updates of their series.
I don't know any magical hashtag as well, I just use the same ones whenever I post
For webtoon #WebtoonCanvas #WebtoonArtist #WebtoonSeries #DrawWithCanvas #WebtoonAuthor #WebtoonCreator
Tapas #TapasApp #Tapastic #TapasCommunity #TapastryTuesday #TapasCreator #TapasComic #TapasticSeries
And so on, sometimes I don't even bother to check if the hashtag is used or if it exist, remember that too many hashtags could lead to your post being "hidden" from search results and such, it's weird in certain platforms and their algorithm.