I'm a self confessed calf cry baby. My brothers blessed with decent (not great) calves and I've got less definition in them than my girlfriend!
I've learnt that these bastards need to be trained every day, or every second day and trained real hard.

My technique is as follows and all work is standing on a smith machine to work the gastrocnemius (because no one cares for the soleus).
I stand with my knees slightly bent on the calf raise platform, squeezing my legs and glutes, this allows me to really concentrate the contraction in the calves. On the down rep I go down slowly and I go a touch past the flat foot point (I don't over stretch) and then I push up a little faster than my downward rep. At the top of my upward rep I hold and squeeze for 2 seconds, then... I PUSH again even harder and hold for 2-3 more seconds.

This gets the calves so pumped that I end up dropping my reps from 20 to about 12 by the end of 5 sets and I'm nearly screaming from the pain

I have done this. Didn't work. I've done everything else also. Nothing works. I hate to sound so pessemistic, and by no means am I intending to shit on your post, but some calves just don't grow, or grow insanely slowly. Mine fall into that group. I've done everything from super high volume 100 reps a day, to low heavy ass calf raises a couple times a week. I've done the slow concentrated reps and all to no avail. I also play strongman, I deadlift, squat, walk with heavy shit, push press, etc - a lot of things that should influence some growth - and you'd think some growth would happen, but nada. After 13 years of training, I've just accepted it. The bastards don't grow.

Also, soreness is not an indicator of progress.

I tried this yesterday. Thank you for posting this. I've tried everything for my calfs and this hurt like hell. I will stick with this and update you in about 6 weeks