I got another tip that might help some guys.
Not sure if you guys ever needed to have a flat sheet of putty for doing stuff on your models.
I ran into this problem some time ago when I discovered a kit with some missing pieces for clothing and needed to make my own repalcement.
A friend recommended using a pasta machine to knead and flatten the putty into a thin sheet and than cut the new part from the finished sheet.
Got myself and inexpensive manual model and it worked like a charm.
Might come in handy for guys doing stuff like zimmerit or similar as the shapes can be cut from the putty “sheet” and than layed onto the kit.
Or the sheet could be layed over a wire frame, etc.
Been using it also to make “covers” for walls cut from foam core.