Probably it all depends of how you will aproach to the trick
My story was exactly the same - 313 and a way later Blind Judge
I started to learn 313 having an airpass in my pocket (i still believe that airpass is a best way to place yourself into handlepasses action). Then started to do an airpass without sending the kite much, then without sanding it at all, then tried to keep the kite bit lower and concentrate on the arms action keeping legs down.
That days i was able to perform 9 airpasses from 10. Transformation it to 313 takes about two hours for me.
The main mistake about Blind Judge IMHO - is thinking that it is an extension of a Raley2blind, while its just a bit different tricks.