IMO i think de difference between lefties n righties is just thier leading hand. For example if ur a leftie n u play de open handed way (left hand leading), its just like de normal right handers playing de crossed way (right hand leading).
If ur a left hander, n u wish to play de crossed way, Its also de same theory as a right hander playin de open way.
The amount of practise is still de same overall IMHO. rudiments also work de same, for example some may play LRLLRLRR but some may play RLRRLRLL, but all these rudiments is still a must to practise in any combination no matter ur a leftie or rightie.