Hiya there. The best way to grow a community in a smaller environment is to comment and favorite other people's content (and on your own) to show that you in fact exist here and aren't just a post ghost. Creating an environment that gets people to comment like creating interactive descriptions and writing answerable journals will help keep people around. Folks tend to not interact/comment with posts they know are from people who only upload and leave because it's assumed the artist won't even be here to read those comments anyways. Gotta put effort into participating in a community for it to grow around you in other words.

Raffles/freebies can also stir up people from the depths of the abyss, especially to help start out being found. Although this would end up giving you more work, doing a freebie sketch from time to time specifically for weasyl users will get people to see you are active on weasyl. I'm on a lot of artsites, so at the begining of the month I host a freebie on one day, and pick out one person from each site who posts.

Art Trades: Weasyl has a very interesting feature called "Collections", and it brings out networking in a way other art sites don't have. When you make artwork for someone on here, you can suggest for them to put it into their Collections. It is an entire folder that acts like you uploaded it, so your watchers see what you added, but Entirely links to the Original creator's post. So if we did an art trade, and I added the art you made me to my collections, all my watchers would also get your art in their submissions feed. Gift art and Art Trades are very powerful things on this site. (Commissions are also included in this, too. If you make art for someone else who exists on here, send it into their collections)

reddit: SO here is one that I use occassionally, is that when i'm quite proud of an artwork, I direct link it on r/furry. This helps people who aren't on weasyl find/discover this site when they otherwise wouldn't have interacted at all. Sharing or mentioning Weasyl helps grow the community a little bit. Especially since the site needs you to confirm new users are real people now (to prevent bot floods).