Bopp or someone more experienced could probably give a better answer than me, but I'll still drop my two-cents.

There is no magic bullet weapon or armor set that can help you through an area in the game, I've found. The best I can do for you is provide a list of gear to consider bringing. None of these are requirements, just guidelines. Also realize that I'm not well-versed in Shadow Snarbolax, I'm only applying my knowledge from other parts of the game to what I believe would be good ways of dealing with those levels.

First and foremost, armor. Mixing and matching is very important here so you can be well-versed. Also remember the ever-presence of Chaos and Black Kat, if you are skilled enough to run this as a glass cannon.

Dread Skelly Shield, Dragon Scale Shield, or Savage Tortoise - Bringing one of these shields is imperative. Status defense on shields is usually more important than damage type defense, so the Poison defense they offer is invaluable. Dread Skelly is the more common choice over Dragon Scale, so I'd personally just go for Dread Skelly, as it's just more balanced than Dragon Scale and better at blocking Howlitzer shots. Keep in mind the movement speed decrease and upgraded shield bash of Savage Tortoise, and also that March of the Tortodrones is just around the corner, if you feel like grinding to get enough glyphs and building materials to make a Tortoise shield.

Radiant Silvermail - Split Pierce/Shadow defense with no Normal defense. It's very imbalanced and specialized, like Dragon Scale, but this would be one of the only areas it works well in (apart from Heart of Ice, possibly). Keep in mind there's no helmet for this armor, only the bodysuit, so you'll need to mix-and-match here.

Sacred Snakebite Pathfinder/Shade Armor - Piercing/Normal defense with Poison and Shadow/Normal with Poison, respectively. Only go this route if you are gonna use at least one or two guns. These armors' brothers, Guerilla or Ghost armor, trade off blanket gun damage for Beast and Undead damage bonus respectively, making them better-suited for this situation, but much worse in the long run.

Shadowsun - Again, a gunner's option. Normal/Shadow defense with Poison, no Piercing.

Fallen - Normal/Shadow with Poison and Fire and all weapons ASI + 1. Make sure your teammates are capable of taking out the Silkwings for you, as it has a nasty Fiend damage penalty. Otherwise, it should be decent here, not great, but it also reportedly works well in a few other areas such as FSC.

Valkyrie - Normal/Shadow with Poison and Curse and Fiend damage + 2. I've never seen anyone using this, but it can be decent here, possibly also in Shadow FSC, if you have ways of dealing with the nasty Fire vulnerability.

Dread Skelly Armor - The shield is much more useful, but it could be decent in this particular area. Keep in mind the many, many alternatives you have.

Skolver - Normal/Piercing with Freeze and sword damage + 2. You'd be wise to mix this with some Shadow and Poison defense.

Weapons-wise, you have a lot more freedom.

Any trusty Piercing sword, gun, or bomb - Flourish or B. Thorn Blade, Callahan, Gilded Griffin, Blitz Needle, Riftlocker, Savage Tortofist, or Dark Briar Barrage are going to be the lifeblood of your arsenal unless you take a support role. There's also always the trusty Iron Slug as a Normal damage alternative to Callahan, and Volcanic Pepperbox to sub for Blitz Needle. (mind the Pepperbox's extra knockback, which ultimately lowers damage potential)

Something to kill Howlitzers - A non-Shadow Pulsar-line or Alchemer gun is the best avenue.

Something to kill Zombies - I'm not sure just how many Zombies there are in Shadow Wildwoods, you'd have to ask someone more experienced, but whatever you use as your main FSC weapon will most likely translate here.

Crowd control bombs - Nitronome/Big Angry Bomb, Shivermist Buster, or Voltaic Tempest/Stagger Storm. Typically, you won't need more than one or two people using bombs like this, so you might be able to free up a slot if you skip this one.

Dark Briar Barrage - I have yet to use this bomb in its five star form, but Bopp and others stand by it as one of the best weapons in the entire game, even if you bring a Piercing sword or gun as your main weapon.

Be mindful of the weapon choices of the rest of your party and cooperate with them. Also consider trinkets such as Pure White Laurels or offensive trinkets (you'll need to do lots of pvp to get those unfortunately), and keep in mind your Battle Sprite's perk and harness.

I hope this helps get you on track.