Select by Material & Hide All Unselected

Material Selection（Material Selection） Animation Tutorial
If the paint bucket is currently the default material, you can select all objects; if the paint bucket is a different material, you can ignore the influence of the group and select the surface directly based on the material. Note: negative material cannot be selected!

Hide All Un-Selected（Hide All Un-Selected） Animation Tutorial
Unselected faces can be hidden without destroying the organizational structure in the model. The hide function can also be used as the hide unselected function.