(Should you decide to include) forearms — how to train the flexors vs the extensors

I know it’s not really necessary to include direct forearm training, but I like to do a little at the end of a couple workouts a week. And, my goal is strength/mass. My program consists of two 6-week cycles (each cycle contains different exercises) following a periodization scheme based on percentages of one-rep-maxes and/or relative insensity — culminating in week 12’s max attempts. This has my training structure ranging from 3 x 10 @ 60% to 4 x (1) 2-5 @ 90-95 % (100%)…with the mean training at 3 x 7 @ 70%.

Generally, I’ve found the flexors respond better to relatively low intensity and high volume (e.g. I currently do twice a week 4 x 15 @ 80 lbs Standing Behind-the-Back BB Wrist Curls). In the past when I tried to do low volume and high intensity (e.g. 4 x 5 @ 85%) it seems to be too awkward and I can’t even perform one proper rep, as if the (near) maximal strength is very poor in that area.

Anyway, I’ve always had difficulty training the extensors, as they seem to be a much weaker muscle and also more awkward to train. Can someone suggest to me what they’ve found to be effective ways to train this muscle? Fast-twitch with low volume, high intensity? Slow-twitch? etc.

Thanks a lot everyone.