Is there something I can add to J-Lube to make it more of an easy-to-wrangle gel?
A lot less water, perhaps. But that makes it harder to mix smoothly (you get clumps in it).
In my experience if you mix it strong and you get lumps just pop it in the microwave and warm it through the lumps will dissolve.
I wrote Mr. S Leather about it, they said melt Crisco in water (1:4 ratio, e.g. 1/4 cup shortening to one cup water), then stir in powder, and then chill in the fridge. That'd cut down the stringiness.