2 sets of seated preacher curls every other week with my ass ON THE SIT in strict form.
EZ curl bar with fat 45 lb steel cookies on each side. (110lbs) 2 sets, yesterday got 17 first set, 15 reps 2nd set. Sometimes I'll throw in a set of dumbell curls, 70-75lbers, 6-8 reps.
I don't have arms over 18 inches but could lift more then 99% of people that do when it comes to biceps.