No problem if all that is copy of components ?
Just edit one instance or a little more complex
Create a new component, select all goto the Components Menu / In Model
RightClick on the icone of the new Component: Replace Selected
If all that is copy of groups Thomthom plug Selection Toy can save you!
@unknownuser said:
Convert into Components - Converts all the group copies into components. Transformation and materials will be transferred.
Useful for when you have a model where groups where used instead of components.
So you will can modify one component as above 😉
If not that is another "rookie error" 😄
If all that is not components or groups
if you are very lucky maybe right click on a white face / Oriente faces do the trick in one time
That will say that you have made a curious modeling 😉
(but I doubt)
In last chance Fredo 6 has made a plugin Reverse orient face who can maybe help you
in a hand workflow
At the end maybe some TIG plug can make something like fix reverse side Material ?
If all that don't make the trick, your last chance is a persannal plug cooks by TIG with
maybe a special selection of a similar face ?
Bu we must wait more details of the situation 😄
or maybe a file skp