Well I tried sanding my disc today.
I did it on the bike.
I tried mesuring runout but the front end was noving around and I could not get a accurate reading.
Miked the disc on every spoke and noted mesurement, ad about 1.5 ish difference. Caliper is also dragging on high spot.
I sanded it with 100grit on a drywall sanding pad. The discs are hard, 10- grit looked pretty smooth, could use coarser grit, be faster.
Anyway took a bit under an hour to get a third of the disc down about a thou. still dragging a tad, but what a world of difference.
Well I got to say it was worth it, and would take half that time with a coarser grit and having the wheel off so you can press harder.