You don't give enough precisions about what is your object: what sort of material you use, have you unwrapped your mesh, etc... but basically if some parts of your object need to be glossy and you can't use the topology to assign different materials to different faces, you should use a Mix Shader to mix something like a Diffuse (or whatever) and your Glossy (or whatever more compex mixes of nodes of course). Then you'll use the Factor socket of the Mix to determine what part will be glossy of diffused, for example a Noise Texture (if you're ok for a procedural texture, make it B&W because the Mix factor needs to be B&W), or an Image Texture (Non-Color mode) if you have unwrapped your mesh. It would give something like this:
