speaking mostly from personal experience - i'm more likely to check a comm thread if it advertises either bundles, sales, or some sort of seasonal thing (like a ych that suits recent/upcoming holidays. i loooove ychs lol). not only does it entice me to look at what sort of bundles they have, but it also shows me the artist is on top of dates and still actively updating their thread, even if it hasn't been replied to in months. (by "bundle", i mean something like "buy 5 sketches, get 1 half off" or something.)
i will note that, in my experience, PWYW art doesn't get as many hits as fixed price art. people are uncomfortable "deciding" the cost of their comms themselves, and are scared of lowballing (even with starting prices) and accidentally offending the artist. a tier system might work better - i.e. $3 nets you a sketch like this, $6 gets you some color, buy four $3 sketches for $10 etc. you'd have to decide those tiers for yourself if you want to implement them.
i think it's also helpful to scrounge the forums for LF (looking for) art threads, and don't be afraid to post your comms there. whenever i had LF threads up i would barely check other threads, but other people's mileage may vary. if you're on multiple sites, check their forums for LF threads and pop them there, too. sometimes i'd scroll other people's LF threads on, say, flight rising; and i've bought off those too.
also - it just helps to be prolific. posting on the forums a lot, maybe bumping your art shop thread with new images you've drawn (comms or personal art). not only does this make your thread look active and keep up-to-date with examples and posts, but also keeps it high up in the forums and therefore more people are likely to see it.
good luck! :>