Update!
The park director wants us to go ahead and try the warm soak + Vaseline treatment for the mites and permethrin/poultry dust for the lice first before contacting the vet. So no vet insight yet, just winging this (no pun intended

) on my own based on the advice I've received here so far!
The treatment stuff all just arrived today and I am hoping to get some help slathering chicken legs sometime in the next week on a warm evening. We will be doing a big coop clean out to replace coop bedding and spray the interior of the coop/roost with permethrin sometime later this month. The permethrin is mostly for the lice, but I read it can help with mites too. I hope it's okay to start treating the scaly leg mites now even though it's still the old bedding. I read they are pretty slow to re-infest and spread, so I hope the girls can hold out.
I've been trying to do research on BYC about how often to treat with Vaseline and have found everything from daily for 3-4 days to once and then again 10 days later to get any eggs that hadn't hatched yet. Any tips? I've never done this before. Not sure if I can do it daily on 10 hens who aren't used to being handled. That sounds like an all day job. May have to just do it once now and again in 10 days and hope for the best.
Someone also said you could spray permethrin on the legs first before Vaseline to ensure more death and fewer treatments. Is that still advisable? It was also suggested to scrub gently with a toothbrush to loosen the debris before applying the Vaseline. Dunno how this helps, maybe exposes more mites? Encourages faster healing and scale regrowth?
Should I soak, scrub, spray, and slather? What a catchphrase.
Sorry, I know this is a lot of questions. I just want to make sure I do the best thing for them.
Last question: A couple of the girls have feathered feet and I am worried about how much gunk their legs are going to pick up being covered in Vaseline since they spend all day in a dirt floor run and have deep litter pine shavings in their coop. Any advice on that? I'm going to try to apply it at the end of the day just before they go roost, so hopefully it'll be on there long enough to suffocate the mites overnight. They roost in the rafters so I unfortunately can't reach them to go do it at night when they are asleep.
I appreciate any and all insight anyone has to offer on any of these questions, thank so much!