With overhangs/bridges, you eventually get into the habit of just trying to design a part so you can avoid that. Sometimes, of course, it is unavoidable. But it is quite strange and nice how your brain starts to just morph use cases into a shape and orientation that makes it easily printable after you've been thinking in the problem space for awhile. Eventually you just end up baking up creative printing solutions that try to avoid the need for supports entirely where possible because introducing supports introduces so many downsides from not only the material cost, but also the aesthetics, time, and frustration perspective as well.

XTC is a good solution for some use cases, and quite bad for others, as outlined above. For the use case in the OP, probably it would be quite nice. That use case is one that is hobbyist level of output in terms of number of units generated but also one where aesthetics are quite important if not fundamental to the overall design. For this kind of use case XTC is a good fit.

The one other thing to consider, if you design to use stuff like XTC and even the urethanes I mention above, is that obviously it takes up some amount of space. So you have to factor that into the design. Probably what I would do is take my boundaries from the original design and increase the tolerance by maybe 1mm or so for the extra space the finishing agent will take up. Because I highly suspect that if you applied XTC to the dock in the OP that the phone would no longer fit after that due to the tight tolerances in the design without that adjustment.