Did you already read this avr-libc: <avr/pgmspace.h>: Program Space Utilities and this http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=38003&start=all&postdays=0&postorder=asc?
BTW: do you think my explanation of the approach here Persistence of Vision | Blinkenlight is helpful?