Im new in blender. Im using it like for a month now and have been focused on rendering fencing stuff like gates, wicket doors etc. but in the past they were supposed to be one colour and stl files i was using were exported without any additional parts like door handles, bolts, screws etc. so it was easier because i didnt have to separate all these parts from the gate. But right now i have a stl file that was exported with all these additional parts and i have to change the colour of those so i need to separate them somehow from that gate so i can change their colour to metallic. I was trying to do it by going in to edit mode, then selecting wireframe mode and selecting parts i want to split using "b" on the keyboard. Then separating by selection. The problem is this stl file was exported in AutoCAD i think and it has so much internal geometry. For example if i separate the post from the gate it still leaves like a half of the screw inside the gate and it takes hours to separate it correctly. I only want to render it for a visualisation so my render doesnt have to be 100% perfect (it is not going to factory and its not technical drawing) but i still dont want it to be so messy. Do you guys know any way i can separate these parts from the main object?