Apologies for the slightly blurry picture but this is the only one I have showing a similar sort of damage. It was sanded to a smooth finish, then the damage was added back on. If the damage had simply been done while it was in progress those sharp edges would still be blurry and not quite straight. That would have a detrimental effect on the finished look.
Currently I don't see any damage on yours at a glance, just unfinished sanding as both side have rough patches and are the same colour.
I've blocked out where I think you were aiming for the lightsabre scar to be in white - leave that section alone for now and go back in and sand down all the sections I've outlined in red - I work through about 5 grits of sandpaper, with the last one being about 2400 so the finish on the helmet is ultra smooth. Make sure all the lines on edges or raised or indented sections such as the visor edge are straight with no loose bits of fibreglass or material.
When painting damage it is always wise to use a complimentary colour to draw it out if your top coat is too close to the damaged section. So if you are going for a grey/black which would blend with silver metal once the silver is weathered, there's 2 good options that will help to draw out the damage. 1 Is to switch the base colour of your beskar to copper or bronze instead of silver. The 2nd option is to use a layer between the silver damage and the grey/black topcoat and have chipping round the edges of the damage that shows off the other colour.
