are there and tutorials here that show how to generate grime and scratch textures for a model? after watching the shading course and seeing kent use the textures made specifically for the gizmo it feels like anything else would be sub par.
if there isnt any is there any chance of getting one??
I would suggest to use Substance, but it comes at a cost. Only way to get truly pro work in short time, imho.
Substance is also my recommendation. but you could also create them using something like Photoshop or an image editing program. It would require more manual work by using brushes or possibly filters but it shouldn't be too tough, especially since these types of textures don't have a very specific look and shape.
bbeast Substance Painter can be used for manual painting, or procedural texturing. Usually you can apply a fill layer that will paint the object with a special type of effect. You can then add effects for grime, rust, dirt, etc procedurally. It detects things like curves and general features of the object to do this for you. This course Texture Weapons in Substance Painter and this course Blender and Substance Texturing Workflow will get you started with how to create procedural texturing along with custom texturing you can create by hand.
If you're looking for the 'quick n' dirty' solution GIMP is the answer. You'll need some good texture workflow tutorials to get started and GIMP has a bit of a learning curve, but not too hard if you just need some convincing scratches. Also scratch brushes abound on the web if you need more options.
However! if edges is all you need to affect, the geometry node pointiness value is your new friend.
Hope that helps.
Oh! last note, Another option,
you can texture straight inside blender with, again, some good tutorials: Blender GURU's Anvil Tutorial | beginner texturing
Hope this isn't too much scattered information and is actually helpful.