Is there any way to increase the chances of a pet having visible traits when you encounter it in the fest zone? or is it just luck?
I'm hoping there is something as I want to go for all 20 on the scavenger hunt and it will be easier if there is a way to influence things

I don't think there is a way for traits, but for some of the tasks, like the Sylvorpa and Kelpari ones, I can recommend to search on the lake, since they're the only Sylesties spawning there. Though I believe Nephini can spawn as well, but I might be wrong on that!

Actually I just remembered the hunt quests in the Grove if you've got the hunting hut unlocked! Those are always rare and higher (daily) or epic and higher (weekly)! Reading through the rules I think you can catch them anywhere.

In fest zones there is nothing that it influence finding pets with traits. Only pure luck can help you.

I don't think there is one, its just purely on luck. going into every battle, or at least the ones you want the vis trait on and hoping the rng is nice T^T

things that I have seen
not that these are a guarentee, nor a way to get more vis traits to show up, but maybe doing a lot of egg hunts and watering flowers for them to bloom?

egg hunts only rare critters spawn (from what I've seen) and those can have a vis trait. not always, rng based like before on other spawns, but they usually can have some hidden stuff if you wanna try to breed the themed pet or sell it for some extra gold to anyone who wants it (a bonus type thing)

watering flowers have the benefit of flower fairies (which drop items and they can be good. still a rare spawn but worth battling. lvl 60 is usually the min lvl you wanna be at to fight them) but they can also spawn rare pets too (still rare, but still there) but it has the same points as before. all rng based on if they will have a vis trait

but I get that pain, I have a few more vis tasks and I am not looking forward to them T^T o7