You can drag and drop a single channel shader onto the item, (each shading domain will highlight in red)
In the shader tab (list) you can drag a single shader, and drop it into a shader channel, then drag and drop that icon onto the next channel down until they’re all the same.
NOTE: If the shader is texture based,. then depending on the model, and the way it’s been mapped, applying the same texture to al pats may not produce what you expect.
it also helps if you say what model you’re working on.
Hope it helps