heres the two i use the most for the best burns ( created by myself)
first one is: go on an incline bench (45 degree roughly, whatever ur preference, i usually do it at 35-45 degree). Grab a heavy set of dumbells u can normally curl like 8 times, lay/sit on the incline bench, do about 4-5 reps of normal curls (dont matter if u suppinate/pronate ur wrists), then do about 4-5 hammer curls, so its a sorta-superset. i find i get hugggeee burns with this
#2: pretty much 21's, but take a heavy barbell used for curls, do 3 half curls like from ur legs then to half way up, then do 3-5 full curls, then do 3 half curls at the top (liek from ur chin/chest to halfway down)
i normaly do 4-5 sets of each, then do anotehr 4-5 sets of normal 5x5 curls and preacher curls and the like.
hope this helps, i no i get siiiiick burns from #1 and #2, number 1 especially