I usually dust one feeder with calcium at every feeding, and about once a month I'll dust two or three feeders with my vit D supplement calcium.
I use Repashy products, their Calcium NoD and Calcium MeD. I've used rep-cal in the past, but have heard complaints particularly from dart frog keepers that it's no good.. apparently the phosphates are pretty high as it is made from ground up oyster shell (if I remember correctly).. however their products say "phosphorous free", so.. *shrugs*
I do not gutload any of my worms, many people use nightcrawlers as a staple for horned frogs with great success, and you can look up the nutrition for the other worms on chameleon forums. It's all great stuff for froggies.