Big Idea: I already have a workbench mounted vise, so all that was needed was a way to suspend the bicycle by attaching it to the vise.
Since my bicycle seat post diameter (and also many other bicycles) is about 27 mm AND the outside diameter of standard ¾ inch iron pipe is just barely under 27 mm, I just removed and replaced the bike seat post with a 5 “ long , ¾ pipe nipple.
A 90 degree elbow connects the nipple to a 18” long section of pipe creating a “L” shaped arm. The longer pipe is then clamped in the bench mounted vise - rigidly holding the bicycle about 6 inches off the ground (see photo).
Step 1: Check Bicycle Seat Post Diameter
To check your bicycle's seat post diameter, here's a URL (http://www.sheldonbrown.com/seatpost-sizes.html) to a bicycle seat post diameter database, or just measure your bicycle's seat post diameter, or just buy a 5 or 6 inch long 3/4" pipe nipple to test fit.
Step 2: Buy Hardware, Assemble, and Test
90 degree elbow,
5" lg pipe nipple,
18" lg pipe threaded on at least one end
Total cost < $10 @ Lowe's (see receipt photo)
2) Screw the pipes and elbow together to create a giant "L" arm
3) Replace the bicycle's seat with the short end of the "L" arm, and tighten the seat mount screw. Avoid over tightening the screw as this might make it hard to reinstall to bicycle seat.
4) With the "L" arm now attached to the bicycle, clamp the long end of the "L" arm in the workbench vise. Position bicycle and vise so you can spin the pedals while working on the bicycle. Most vises have a pair a semi-circular jaws below the standard straight jaws for clamping round objects.
5) That's all there is to it !