You can perform what is referred to as "21's".
Assuming you have a training partner, have your partner place their fist on your sternum. Do 7 curls, touching their arm on the way up and counting to 2 on the return down. After 7 reps, have your partner remove their fist and complete the curl up to your chin.
While the bar is at your chin, have your partner place their fist back in your sternum and lower the bar back to their arm, controlling the weight on the way down. Again, do a two count down to their arm.
After 7 reps, have your partner remove their fist and then complete 7 full movement curls, this time aim for 3 second controlled count on the down. Your arms will burn like you probably haven't experienced before, but do this for two or three sets and this should bulk your arms up in no time.