the RS4.2.1 comes partly pre-bedded out of the factory and as such needs only around 150-200miles max (combined with the discs) of reasonable driving..................
don't molly coddle or they will never bed properly, but no ABS type stops either!!
DO NOT be attempted to use the aggressive bedding process with RS4.2.1 as this is only for more competition orientated materials and definately will cause problems with discs...................
you always need to bed the components you have properly (in the manufacturers spec) rather than some posts on the web that suggest that every material/scenario is identical..................
hope this helps, alyn