Help to cut mesh

[system]

Hey guys. i really need some help to continue my model.
i’am all new in Zbrush and i just imported my clean mesh from 3DS max and now i want to sculpt damage and rust.
i really dont know how to make rusted areas where the metal is all gone i made a picture in Photoshop so you can see what i mean the left one is my model, the middle is how it looks now and the left is how i want it to look… made in photoshop

how should i make those cuts in my mesh inside zbrush?
and should i make the details in dynamesh or zremesher.??
thanks in advanse

Attachments

[Morgus]

So, Im not super expert, but I would use Slice Curve brush, draw out your contour with one stroke or you can overlap strokes and it will assign new polygroups to the cut pieces. I think you can hide the polys that arent around this to limit where the slice will change topology to the visible polys. Then delete the piece you want removed, either hide that part and “delete hidden” or use zmodeler and delete polygroup island