Butternut has no bumps. Jiminy has almost no bumps, but the extremely few bumps are steep.
Catamount has very good bumps, which is where I started learning bumps. They have a black, Offstage, which is very tiny moguls on a pretty flat surface for a long time, until the end. In the end, the moguls are big, icy, and the terrain is around steep blue. But what I did when I learned bumps was go down the run until the steep part comes and then turn off the bumps (only 2/3 of the run is bumps; the other 1/3 is flat). Great place to start learning bumps. Then, after that, you can go on Lower Glade, which to the far right of the run is tiny miniature bumps, in good condition, on a moderately steep black surface. The moguls are tiny so it's a great place to learn after learning the top of Offstage. After learning Lower Glade, head to the bottom of Offstage, but start out doing the moguls slowly. Then head to Catapult, the signature double black there featuring average sized moguls on a steep double black surface.
Belleayre also has good bumps. All the double blacks there are moguls on a moderately or lesser steep black surface. Onteora is the best learning bumps in the Catskills and Berkshires(on average throughout the entire run), being a black with medium sized bumps on a greenish blue surface.
Hunter is after you have mastered these two mountains for moguls. Hunter is STEEP, ICY, BIG, AND OVERALLY NASTY MOGULS.
I would recommend you try both, and then Hunter. I started learning the bumps at Catamount on Offstage and Lower Glade. But I got good at it at Mount Snow, VT. Upper Challenger is the funnest moguls in southern VT (the funness of the trail just kept me going and going on that run!)!