Having made my living by cutting a ton of dovetails, my method is to use diamond stones and either free-hand the bevel or use one of those 'roller things'. I personally don't feel a hollow grind is necessary. No two woodworkers do it the same way it seems, so differing opinions abound. First make sure the back of the chisel is flat by rubbing it on the stone, then proceed with sharpening. The only other advice I would offer is that when using them don't let them get so dull that you have to go through the whole schmear again. When it starts to lose its edge, stop and hone it. Chopping dovetails will dull it quicker than by using it to pare.
I have one of those grinding machines, but I only use it to restore a nicked or otherwise destroyed edge. Then its back to the stones.
