Crushing the jora is not easy. The roller mills usually used by homebrewers (MaltMill, Glatt, etc.) will not work as the kernels are too big.
One solution to the problem is to make a big mortar and pestle out of a stainless steel kettle and an unpainted 2.5lb aluminum CO2 cylinder. While this method lacks the appeal of automation, the jora will be reduced to mostly flour fairly quickly.
The best way to crush jora is, of course, to use a Corona mill. It's possible to find them for not much more than $20 and many homebrew shops have them for around $40. Worth considering if you're going to do more than one batch of chicha.
The jora should be finely crushed, almost completely to flour.