I think for almost everyone it boils down to gentics and how they grow. Benj is nothing but arms so all he has to do is rub one out and they grow, Me on the other hand have to train them twice, once by their selves and once after back.
I do a arm workout all by itself once a week. Bi's and tri's usually at the end of the week and I destroy them 2 hr workout..legs the next day to give them a break.but between chest , back , and shoulders it's like 2 bicep and 3 tricep workouts a week. Its a bit much, but I can get them pumped up to 22 inches.
I'll do 3 sets of either barbell curls, incline db curls, single arm cable curls, even burnouts at the end of a Back w/o. I switch it up often.
Every couple weeks when I'm looking for a good pump I'll dedicate one day to arms.
I do my arms on a separate day. Usually following a shoulder day. Just seems to blow the shoulders back up. I start with Barbell curls and do 4 sets with one warm up set of 15, then 10,8,6,4. then I will do incline DB curls 4 sets of 8. Then I will do standing alternating DB curls 4 sets of 8. Then I will do concentration curls 4 sets of 8. Then I will move on to triceps. Start off with scull crushers 1st set warm up for 15. Then 10,8,6,6. Then I will go over to cable press downs with V-grip and do 4 sets of 8. Then I will do standing one arm ext. over the head 4 sets of 10. And then hit the shower. been working great for me.