So, what did we learn about this witch?
1. That "eye" is actually an air intake valve and we probably shouldn't attack it in melee.
2. This thing's fucking fast.
3. Its two middle fingers are ranged weapons.
4. Sukuyo's regular bullets, and a flaming shotgun shot, just bounced off of it.
5. It attacked via punches, flicks, and by shooting musical notes.
6. A punch is not enough to break through Sukuyo's DR.
Grabbing things and shoving them into the air intake valve to be mulched seems like the most deadly attack it has. Followed by Shooting notes and high speed punching then finally stationary punching and finger flicks. Coupled with its high speed and being a large hand, getting grappled by this thing is almost certain death, as was elegently shown by Akane getting mulched. As for dealing with its regular attacks, that's just up to the dice. There's nothing special about "dodge the musical notes before they cut you" and "don't get hit by the witch's melee attacks."
As for actually dealing damage to this thing, I'd still target the thumb first. Because we never actually saw what it could do and I'd rather never see what it could do. Then probably the recorder fingers to cut off the ranged attacks. Yoko could try and jam the air intake valve, but if that thing can just grind down what it pulls in, I'm not sure how effective it would actually be. I suppose this strategy largely depends on how strong the air intake valve actually is more than anything.
The newbies on the other hand...Pretty sure basic crossbow bolts and regular ammo won't cut it. Basic crossbow bolts might work, because they're more piercing than regular bullets, but all of Sukuyo's basic shots bounced off. Tomo can at least accel her bolts so she should be good. Sukuyo...could probably just make a bigger gun and she'd be fine as well. Yoko should probably focus on tripping up the Witch or trying to block, or at least slow down, the ranged attacks and melee attacks.