Here is my tip, Don't use a carbide burr unless you are roughing.
Carbide is fine, but it is really hard to control. It is amazing at it's job and that is high material removal rates but it is not a be all end all bit.
What you want to do is if you have a lot of material to hunk away, start with a carbide or HSS burr, then swap up to a nice diamond dental burr.
With the diamond dental burr you have amazing control. It is so easy to just not have to worry about it grabbing and rattling around a port. Plus they are cheap.
I use this cheap aliexpress dental handpiece, I have gone thru one set of the "tips" but the motor and controller are still kicking. Key is to lube it a lot, like every hour or so lube them
bits you want diamond burrs like these.
those are 2.35mm shank, also note the 90* hand piece required latching D bits, but I usually just grind the D into it and superglue it in, then tap it out when I am done. You can also find these in the standard dremel size as well.
After that practice, practice, practice!
Having a few small diameter sanding drums are also very handy for large flat things.
some of the key points are trying to change direction and pattern often to avoid divots and help with removing high spots. If you follow the same side to side pattern it's easy to create wavy divots that are hard to remove.