How to create a DLL library with your own element styles?

Question

C++ / C#

Hello, you need to make a DLL library, when connected (in WinForms), the style of the Button button changed.
What is the easiest way to implement this? I understand WPF and UserControl is not what I need?
You need something like the MaterialSkin NuGet package, when you connect it, new element styles appear in the ToolBox.