Thought I should add some pics of my sandpaper sharpeing station.
Last winter I had made this sandpaper sharpening station. This station uses a piece of plate glass about 6"X36". Strips of pressure adhesive backed sandpaper are applied to the glass, and chisels are sharpened, starting with coarse grits and working to progressivley finer grits - 80, 150, 220, 400, 800, 1000, 1500 grit. With chisels that have been damaged, are not flat, or have no edge, most time is spent on the 80 grit, and less time is needed with each successive grit. After working with each grit, the tool is wiped off to prevent contamination to the next grit. The paper used is also wisked with a brush or wisk broom to remove any metal or sandpaper dust and prevent clogging of the paper. My blue brush is one that was in the brick/mortar section of my local home center. Just have one that is stiff enough to brush out the paper. Once the first three grits have been worked through, finer paper is laid on top of those grits. These finer grits are NOT adhesively backed. they are held in place by the friction of the sanpaper base. These finer grits are automotive wet/dry paper that can be found in autobody stores or sometimes autoparts stores, and come in sheets that can be cut into 3 pieces. A razor blade holder(on the right of the station) is used to cut the adhesive backed paper to length and the fine grit paper if scissors are not handy. I use a red marker to color chisels and after lapping, I can easily see what has and has not been lapped flat by what marker has been removed. All of my framing chisels are antiques and are all TH. Witherby purchased off of ebay. Some were badly bent and were straightened by Jim Rogers partner in a forge. All of my chisel sheaths were purchased from Jim Rogers as well. My chisels are currently still being prepped with 80 grit but most are almost ready to move to the next grit. This sharpening station can be used for more than just chisels. I've used it to sharpen a hatchet, pruners, loppers, tune ships auger bits, and even sharpen the counter sink on countersing drill bits. Some of the small wood dowels and pieces of wood are used with the various grits of sandpaper to sharpen small or curved tool edges. This is a very effective sharpening method.
Chisels that are in good shape, you usually do not need to go back to 80 grit unless you damage or chip the tip or corner. A tuned chisel that is starting to dull just needs to be gone over from 400 to 1500. Exactly how coarse you start on depends on how it looks and your judgement.
If you've used your chisels when they are sharp and when they are not, you know the difference. You can shave and plane with a sharp chisel. You fight and cuss with one that is not, and you end up gouging when you don't want to. I don't use any guide except my fingers and the existing bevel.