I think this is maybe correlation rather than causality. Promoting your work more isn't necessarily what makes you more likely to get a staff pick.
For example, I used to post in more promo threads when I was new, but I quickly began to see that the promo threads requiring legwork, ie. samples of my content or some kind of interesting discussion around it, or even my review thread, which doesn't link to my own comic, were netting me a lot more readers. Plus, as my subs went up, I was basically locked out of more and more "promote your comic, under X subs!" threads, which are most often 25, 50 or 100.
I was at a bit over 250 subs already when I got a staff pick. It happened almost immediately after I was nominated for a community pick. Maybe the two are related, maybe they're not. I do think that in some cases there's a certain level of visibility that can help you get a staff pick, like if the staff keep seeing your work pop up they're more likely to think of it.... BUT the memorability of those posts is important too. So maybe it went like:
- Staff sees I have a review thread with lots of engagement. Oh cool, good on that user.
- Staff sees me on a promo thread. Oh right, it's the person from the review thread... Hmm, that's an okay looking comic, maybe one to consider...
- Staff sees me get a community pick nomination and the post nominating it gets a fair number of likes. Okay, let's staff pick this and see how it goes, it seems decently polished with good community engagement.
(This is completely hypothetical. Maybe it went nothing like this, it's just to illustrate the idea that just seeing your link is less likely to stick in a person's mind and attach positive impressions about your "brand" compared to posts with more interesting content).
So my advice is rather than getting seen more and becoming part of the background scenery, try to make your appearances count. Make them memorable.