Never much of a problem with bumps in either of my cordovan shoes.
I don't think a mirror-like shine is really possible or desirable with shell cordovan (at least not in my experience). Part of the bonus of cordovan is not having to wax them as much or as often as you do calf. I use a tiny bit of wax paste to shine them about once every three or four months, with plenty of brushings inbetween. They get a nice shine too them, just not something on the level of "mirror."
PS - too much paste can really be a problem - it smears around for ever and ruins the shine. I did this once, and managed to get things back to normal through a combination of time and lots of elbow grease with an old t-shirt.