The phrase "to make a coat" means to create or construct a garment that is worn to cover the upper body, typically during cold weather. Full definition
I think if you add snaps or buttons it might make the coat look like a dressing gown which I don't think is the look you're going for! (acolourfulcanvas.com)
It has the same effect as putting it with their feed, keeps bugs away and helps make their coat shiny. (homeremediesfor.com)
A food with generous quantities of fats and oils from quality plant and animal sources will make his coat shine and his muscles strong. (mysweetpuppy.net)