What McDust said for rough stuff like splitting mauls and first pass for sharpening chisels, knives, planer blades.
A big diameter wheel (8 or 10 inch) can give you a hollow ground edge, with a little practice. Hollow ground makes it easier to hand sharpen to a really fine edge
Stationary belt sander works well, 220 grit belt will get things pretty sharp. You can burn the sharp edge if you're not careful. Keep a bucket of water handy, and dip the blade often.
Haven't tried a flap disc, but I like them for other stuff.
For chisels and knives, after the wheel, lay a sheet of good quality wet and dry sand paper on a sheet of glass, or other really flat surface, start with 220 grit, then 400 grit. Wet the paper with water or oil.
A sheet of the good, black wet and dry paper will last a long time if you sand wet.
For a sharp edge, you need to strop the edge after you sharpen with abrasives. Old leather purses are a good source of stropping leather.
If you want to get into sharpening, a cheap jeweler's loup is a good investment. You can see the sharp edge, and the burr that the strop removes.
If you get your chisel sharp enough to shave hair off your arm, you will be amazed at how much more accurate your wood work can become.