Hi, MyNameIsRay!

From what you say, you have a loose bearings hub with cups and adjustable cones. The races that the balls ride on, both on the cups and on the cones, must be in good shape in order for the hub to spin smoothly. I would dissasemble the hub again, clean the left and right cups and cones, and check for any signs of pitting. If the cones are pitted, get some new ones. If the races are pitted, get a new hub. Of course, the bearing balls must also be pristine. If the cups and cones are allright, stop riding until new bearing balls arrive (make sure you order the same size balls), clean everything, pack with grease, adjust the cones so that there is no play in the wheel but also no drag from over-tightening the cones and see how it spins then.