I grind up one grit higher than I start sanding at...so that means grinding to 400 grit, then starting back at 220 or 320 with paper. A grinder finish hides a ridiculous amount of small flaws. What looks like a perfect 400 grit finish will reveal a much different story once you begin hand sanding. I "scrub" back and forth with the paper wrapped around a 2"X1/4"X20" bar of steel until 400 grit. From there, I only sand lengthwise from plunge to tip all the way to my finishing grit. Windex or WD-40 does seem to make the paper cut longer, especially at the starting grits. The second I can't "feel" the paper cutting, I move to a new section of paper. Like others have said, treat it like its free and you will gain more $ in time saved than $ saved eeeking the last 10% of use out of a 25 cent sheet of paper.
I sand with a bright light over my shoulder, which will show every tiny scratch that needs to be taken down. Remember that when a scratch needs to be removed, you need to remove meat from the whole blade, not just scrub that one spot.
Once youre at 800+ grit, its a zen experience. Don't just lay the paper on the blade or you will get fishhooks where you begin. Lay an edge of the paper down, then drop the rest of your block onto the blade as you begin to move. Its the starting and stopping that will create those annoying fishhooks.
