Blender

Blender wont zoom in anymore - https://www.youtube.com/watch?v=vfHtoBZ-Mv4
Blender wont switch between Edit/Pose/etc mode properly - Edit > Lock Object Mode (OFF)
Blender wont copy textures over - Gotta export fbx as Path Mode: Copy or no textures are included
Blender STILL wont copy textures over - do File > External Data > Find Missing Files and point towards the folder with the .pngs

Show Bones while in weight paint mode:

(I want to easily change between weight painting each bone)

Click on mesh in object mode
Modifiers Tab
It will show you which armature you need, so, You need to select Armature.002, for example.
Click that armature, Hold Shift, Click the Mesh in 3d view (THIS IS HARD AND STUPID, KEEP TRYING)
Ctrl+Click Bone to swap between bones (Might be alt instead of ctrl in newer version)
If its purple, there is no vertex group. Left click & It will auto create it.

"prefab.unity3d does not exist" error is fixed by typing "t:scripts" in the hierarchy and deleting all broken scripts (Like missing dynamic bones for example)
id must be a 'avtr' ID: (UnityEngine.Debug:LogError (object) error is fixed by detaching the descriptor from the pipeline manager
Unity Cloth being weird/spinning is fixed by: If you add Unity cloth physics to your av, ensure all Unity colliders you use have "Is Trigger" checked on. When you use Unity cloth physics on an avatar, you have to use Unity's built in Collider components to control how the cloth lays (rather than VRChat physbone colliders). If you set "Is Trigger" checkbox to true, the spinning I described would happen. However, all colliders I added had this checkbox off, so I couldn't understand why it was happening. Make sure all "Is Trigger" boxes are checked on all Unity colliders. (Thanks Omni)
If the textures look weird in Unity but not blender, make sure to select the TEXTURE (not material) in Unity, and in the inspector under default tab, turn the Max Size up to 8k texture (or whatever) (Thanks JC) ( https://cdn.discordapp.com/attachments/1019158348614082640/1044645271440728094/image.png )
If you type in: t:script in the avatar heirarchy you can see everything that has scripts (Useful for finding physbones / dynamic bones)
Use VRCQuestTools to auto convert all materials to quest materials
If your character is stuck in squat pose, remove the controller.