I have done a few SS and fixies now and normally what i do is remove the axle by removing one side of the nuts and replace it back the other way. This shifts the hub over more to the drive-side.
I might additionally swap some thin washers or nuts around to get the chainline right.
I then loosen all of the spokes slightly and start again making sure the rim is centered properly. This method seems to work for me so far.

I want to bump this thread because this sounds like something I want to try and have a few questions:

1) Will I need cone wrenches to move the spacers or do I just unscrew the nuts at each end of the axle?

2) What do I use for spacers?

3) How do you measure or gauge your chainline? I've never been sure with doing it by eye because of the lack of parallel lines on the bike as a guide. Do you calculate a center point on the axle and the BB and measure from there?

Thanks

Interested as well...

I reset all of mine to 120mm spacing, removed 6mm of spacing from the rear and moved the front ring inboard as needed. Without removing 6mm and going to 120 youll have an oddly dished rear wheel.

Almost every SS conversion in town is a "Lazy Mechanics' Special" - SS freewheel spun straight onto a 126mm rear hub. No redishing, no removal of spacers; just the freewheel sitting too far inboard, accompanied by nearly all the RH hub spacers exposed to the world.

Chainline is almost always off to the left on these conversions, and they're aesthetically disgusting. Nevertheless, they seem to work, and I've been guilty of a few such conversions simply to compete with the local C-list market folk - who have no appreciation for time, effort, or quality.

-Kurt

IIRC, either from BF or Sheldon Brown, a chainline of 50mm is a good starting point. You roughly measure from the centerline of the seat tube out towards the DS of the BB. (if I'm wrong, please correct me!)
Once this is established, you adjust your chainring position, ie. various spindle lengths, dual adjustable cups.

As for cone wrenches, that depends on the hubs since not all hubs are standard hex (lock)nutted. Superbe Pros are machined flats like the cones, Deore hubs are also flats. So, cone wrenches are needed anyway if you plan to re-space your hub. I don't recommend taking a 126-135mm OLD down to 120mm, unless that's the spacing of the frame you plan to use, then it's axle swap time or a hack saw exercise.

Spacers: you can first try swapping the DS and the NDS spacers to see if this brings the hubshell close to your target chainline. Otherwise, one can salvage old hubs for 5 and 10mm NDS spacers. 1mm flat washers will work too.

For a straight edge reference...might try first mounting a well trued and dished wheel on and use the rim edge to rest a straight edge (carpenter's level).
Then measure off it to zero in on your target hub position.