I use 60 grit(emery is best) glued to plate glass and an angle grinder for shaping.
For the back, I'll start lapping on the plate glass for maybe 30 seconds, till I can see what is going on. Then I clamp the chisel in a vise and use the angle grinder to remove the obvious, being aware of overheating the chisel. I'll bounce back and forth between the plate glass and the angle grinder until back is flat. Often there is a low spot just behind the edge of the chisel that can be tapped down with a hammer and anvil(cold).
For the bevel, I use the Lee Valley guide

http://www.leevalley.com/wood/page.aspx?c=1&p=33001&cat=1,43072,43078&ap=1

I had one years ago and wore it out, then went free hand, then recently bought the guide again and am loving it. I use the same process, set the chisel to 25deg, work on the plate glass for 30 seconds till I can see what is going on, then move to the angle grinder to remove the obvious, have to be a lot more careful about overheating when grinding the bevel. I like the angle grinder because I can see what I'm doing at all times, as opposed to a bench stone where you can't see until you take it off the stone.
Once the shape is there, I move to waterstones and finish up. The Lee Valley guide does a good job on the microbevel.