shaders work almost the exact same between 2D and 3D. the only difference is you have a vertex shader before the pixelshader. But for most simple stuff that vertex shader is just passing the vertexs to the pixel shader.
Also all HLSL shaders work the same, so finding an example outside of monogame still works.
You apply multiple shaders by creating a render target, then rendering 1 shader at a time to the render target. Make sure that you do them in the order they are written to be applied and you should be fine.
All XNA Shaders still work in Monogame… you just have to change out the shader version (you can see the pixel shader verison in my 2D shader, and the vertexshader version is the same but with the vertex shader version).
I think that trying to start game dev’ing with the complicated stuff is unwise (you are trying to start at step 50 of 100, rather than starting at step 1), but its all out there to be learned I guess.