I use a Dremel with a diamond cut-off wheel for the housing. No need to dress the cut on a grinder afterwards!

Whatever method you use to cut the housings, make sure you have a clean 90° cut - either in the initial cut or whether you end up dressing it on a grinder - otherwise your brakes will be 'mushy' as the slop gets taken up.

I always leave the inner cable a bit long - so that when everything is adjusted, I can either solder the inner at the appropriate length and then cut it through the soldered part - or in the case of slick stainless inner wires, use a crimp-end.