Fine model, Bandolin!  The final result looks really slick.

"Before going forward with any chamfering, just do a By Numeric selection, at face level, for any polygons with more than 4 sides. If you find any, you can decide how to fix them before continuing. Sometimes it's just a matter of selecting a few verts and collapsing them, or target welding. If the number of sides of any polygon is an even number of vertices, then you can quad it up no problem by cutting edges between the verts."

Good tip, lux, and alludes to the fact that when modelling, we need to think a couple steps ahead always.

One trick is that whenever you create a spline shape, and extrude it to create polys, the ends get capped with ngons.  Most people just leave those in, because they can't figure out a way to quad those end caps, especially if the shape consists of a lot of verices that would be really hard to manually cut edges into.

One solution to this is to make sure, when you're creating a shape using splines, you always consider the fact you can convert that to editable polygon, and use turbosmooth to smooth it out more.  So all you really need to achieve with your spline is a relatively smooth shape profile, which can be smoothed further with subD.

Reduce the interpolation of the spline to about 1 or 2 (default is 6).  This way, you end up with less vertices around those ngon caps, which will be much easier to quad up once you convert it to an editable poly.  Try to find a low interpolation level that provides EVEN number of vertices at the end cap borders when you convert it, and you should be able to cut edges across those end caps very easily to create quads. Then add your support loops, and use turbosmooth or nurms to smooth it out to the desired level of smoothness.

Same technique applies to a lathe or loft.  Don't go for the final smoothing result right off the bat, if you are going to cap the ends.  It creates way too many vertices, and capping the ends with quads is more difficult.  Keep the interpolation low, with the intention of smoothing as the final step.  You can always put a turbosmooth in the stack above your lathe or loft object, and preview the result at various levels of interpolation and subD.

If you have a few bucks to spare, and really want to fully automate the process of quad-capping any hole on any mesh (not just end caps, but holes in the sides, or anywhere), then have a look at the awesome Quad Cap modifier.  I got this one for myself for Xmas, and it's awesome.  Every bit as useful as Quad Chamfer.  You'll never see an ngon on any of my objects again I tell ya.

---

Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.