Predrill an entry point, so that you don't suffer endmill damage attempting to plunge into the cutting depth.
Rough with a stub length flute, coated carbide, 20000 rpm. I'd probably try to rough that out with sidewall 'draft', which would imply a slight angle inwards to create clearance for the rougher as it gets deeper into the work, so that the neck of the cutter does not rub. Set up your CAM so that each pass is about .001 narrower, at about .03" depth per pass.
Switch to a finishing tool and take two passes .125" deep to straighten up the wall. Keep in mind that the first .030" of the rougher gets dulled, so it won't do much of a job trying to finish at .125" deep, due to deflection of the dulled flutes.
If feasible, plan a rotation of the slightly worn finisher into the roughing routine, and then get a new finisher.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)