Id probably copy the settings into a text doc then change all from left to right, then set up the numeric values on the SDKs for the opposing hand again copied from the left but again change the orientation from positive to minus (depending) then just copy and paste each one accordingly.
at first I didn´t understand what you mean by that, maybe because it is the most reasonable solution... I tried to find a way for quickly minus scaling the damn hand and get it somehow into hirarchy at the other side. but I failed on finding an easy way without any unneccessary transform nodes which have odd rotation values themselfs.
in the end i found myself writing down the SDK values into wordpad by hand like you do Jay. but I´m asking mayself if there is a MEL way to automatically get all selected L_joint´s .rotationXYZ values, to store them somewhere and apply them to the opposite R_Joints...?
unfortunately I don´t know anything about MEL. but I got interested in now.
everything starts and ends in the right place at the right time.