Jack,
Additionally, whuke you build your forearms strength I'd make adjustment like I had suggested to limit the pain. Try reverse grip or better yet forgo the barbell for dumbells. The pain is a result of the grip and tension created by the bar. The same tension accounts for the high weight one can handle using both arms at once. Another adjustment would be to keep you wrist suppinate (I think thats the word but basically keep your wristed turned all the way in) through the whole curl. I'd do preache concentration curls and incline curlss with dumbells. Go damn heavy for low reps and do more sets at this weight for limited reps. You will build size. In the mean time, work those forearms so you can get back to heavy barbell cursl which are best for mass. I'm gonna assume you're already using an e-z bar right? Hope this helps bro. Out.