Two questions
 

I've read somewhere on this forum that it is possible to use a b/b lockring to convert a s/s to fixed. How does one do this, and will it work on a cassette that was converted to s/s. I also want to repaint my frame cheaply, but nicely. I would prefer to do it myself rather than pay a shop to do it. Can I simply sand the old paint to get some texture, primer and paint, or is it more complicated that that.

in order for the old school BB lockring trick to work, you need a threaded-type hub (one where the freewheel threads onto the hub). you get yourself a track cog, thread that onto the hub, then thread the BB lockring right up next to it, use some locktite, and make sure it's REALLY tight.

i don't know much about painting...so i can't help you there. someone else can though. lots of folks have repainted their frames.