Armor can be tricky since technically it doesn’t usually deform with the rest of the body. If you consider a knights armor, for example, it’s a solid mesh which is relatively easier to implement but then you end up with a character with extremely limited movements in order to avoid any protrusions.
I’m not sure if this is this will help, but this is what I do. I duplicate the parts of the body that I want to add clothing to and use the solidify modifier. I apply a negative thickness and as long as the clothing shares the same sub-surfacing level as the body, there will be no protrusions and the new meshes automatically inherit the armature deform which you can turn on and off from the same modifiers panel in case you need to make further edits without the deform getting in the way 
I use the blender outliner a lot to show and hide items of clothing depending on the scene I am creating so my characters are wearing their entire wardrobe at all times 
Also, consider using the mirror modifier so you’re not modeling everything twice. Now you know why my characters never wink with just one eye in my animations 
Good luck with your project!
