Smoothing makes a mess of faces

[micheus]

Nice, for CNC that note for 3D printing should be valid as well.
But, if you have to design anything else on the shap, like a hole or cave something, them it's a good idea do that before you smooth the piece because you can create cuts to help you place a polygon on the place to be worked.

About the density, for this use it should not be so bad for your work now you understood how to handle it. Eventually you can do what I did by removing edges that aren't that important to define the shape. When we understand how the subdivisions will be applied we like know where we can remove these edges, slide them to and so on.

Remember you can use Smooth Preview [shift + TAB] to get the Idea about how it's going on.
Also, when removing an edge it's a good idea to use the Dissolve [RMB] that will remove any orphan vertex - that avoids unwanted issues after removing edges.