Partial mashing will require you to be able to maintain mash temp long enough for conversion which can be a little tricky on the stove. I suppose if you have one of those little 6 pack coolers you could mash a few pounds of grain in that with some stability. Otherwise do you best on the stove top, when you have converted your starches you will need to sparge as you said...I only did this a few times before saying screw it and going AG...I did this buy putting the grains into a colander and slowing pouring 170 degree water over them.