finishing your arm workout with hammer curls hits the forearms pretty good, specialy if you dont relax your grip at the bottom of the movement...
an old gym i went to used to have a broomshank with a peice of rope attached to the middle, you used to tie a dumbell or disks and roll it up to the top then roll it down, wringing your hand one direction one time then the oposite the other set,,, most horrible burn youl ever experience!
on the subject of arm training, ive allways went the low set route, its more important then any other bodypart to not get carried away with the weight imo, more so with biceps than triceps.. my fave workout would be( with fresh elbows and shoulders)
seated alternate curls 3 warm ups, one full set 8 to 10 reps
standing straight bbcurls 1 warm up 2 full sets 8 to 10 reps
hammer or preacher curls 2 sets, moderate weight
tricep pushdown straight bar 3 warm ups, 1 full set
seated ez bar extensions 3 warm ups, 2 full sets( this can play havoc with your elbows, dont use it anymore, still my fave for putting meat on)
seated db extension 2 sets
dips one set, rest paused till i can only get one or 2 reps out