Actually, there is a way to cheese JC still, if you just want to skill it up: make wires. AFAIK you can make any recipe in the game, even if it's not yet on the list because you have 0% chance to succeed. So you make copper wire until its green, then move to bronze, then iron, steel, and finally mithril. When the previous wire goes green, manually put in a single bar of the next tier and hit combine. Fails still give skill ups.
This should work for every tradeskill where there is an easier/cheaper higher level recipe that is 0% success rate.
